■ pkgsrc and SunOS 
As I'm slowly becoming well-versed in running pkgsrc outside of NetBSD,
I couldn't help falling for the challenge of deploying a pkgsrc-based
desktop on my Solaris VM. All things considered, this was one of the
main purposes which drove me to install Oracle Solaris in the first
place.

Few years ago, I was running OpenIndiana on desktop and getting
additional software from either OpenCSW or pkgsrc. In my experience,
after NetBSD, Illumos is possibly the best platform where to run 
pkgsrc, reflecting the effort put by Joyent and the SmartOS folks in
delivering a reliable product. Prior to that, J.Perkin had already done 
extensive work on pkgsrc and Solaris 10, with the intent of getting a
unified framework to manage third-party opensource software on Sun's
UNIX.

Looking at pkgsrc packages, and skimming through  patches and platform-
-dependent flags, it's not hard to deduce how most of the work done to
adapt pkgsrc to SunOS was carried out on either Sun Solaris or Illumos.

But what about Solaris 11?

By the time it came out, Solaris 11 represented a huge step forward (or
sometimes, behind) Solaris 10, in spite of the fact it kept backward binary
compatibility with its parent version. Solaris 11 has diverged 
a lot from illumos over the course of the last decade, and this is all
the more evident in Solaris 11.4, which presumably backported and merged
some of the things which were scheduled to come to light only in 12, the
lost version.

This is to say that was I not expecting to have a smooth experience by
attempting to deploy pkgsrc on 11.4. In retrospect, I won't deny I've
been at least partially proven wrong. pkgsrc bootstrapped fine at the
first attempt and several packages built flawlessly. Many other, however,
required  minor fixes and adjustements, and some were broken beyond my
capabilitites. My suggestion is: do this only if you have time to spare,
for learning, for fun, for testing / bug-reporting, and if you want to
contribute patches. 

■ dependencies 
In order to bootstrap pkgsrc on Solaris 11, common requirements are:

pkg:/system/header 
pkg:/system/linker
pkg:/system/library/math
pkg:/library/glib2
pkg:/library/libxml2
pkg:/library/zlib
pkg:/developer/library/lint
pkg:/developer/object-file

And naturally, a compiler.

On Solaris, you usually have two choices when it comes to toolchains:
Solaris Studio (formerly known as SUNPro and SUN Studio, now known as
Oracle Developer Studio) and GCC (historically available via
third-party repositories like sunfreeware and CSW, now included in the
official repo). Spoiler: 11.4 also supports and provides LLVM. 

Plenty of choices then, so what to use? According to my own -limited- 
experience, it is advisable to get both Studio and GCC, regardless of
OS version.

Noticeably,Solaris Studio is designed from the ground up to play nicely 
with the only OS it runs upon. Whenever a piece of software is built
with portability in mind - especially if it officially supports Solaris -
you can be almost sure it's going to build just fine with Solaris Studio.

[EDIT: it would appear that newer versions also run on Oracle Linux]

However, some software will still expect GCC, so it's good to keep a
well supported version of the GNU compiler always at hand. Also, GCC is
visibly faster: this may be partially due to Solaris Studio not enabling any
optimization by default and/or open-source projects catering their
compiler flags to GCC. 

■ GCC
Installing GCC-7 on Solaris 11.4 is as easy as:

$ pkg install gcc-7

This will install the compiler at /usr/gcc/$(GCC_VERSION)/bin and
synmlink it to /usr/bin, so that it will be automatically made available
in users's $PATH. Many other versions are available (from 5 to 11,
skipping few versions in between). When bootstrapping with GCC, GNU
binutiles should be also installed (available as
pkg:/developer/gnu-binutils).

If you want to bootstrap pkgsrc using any version of GCC but that 
associated with /usr/bin/gcc, then the CC environmental variable should
be pointed to the correct executable, and GCCBASE set to the
corresponding version's dir under /usr/gcc (i.e. GCCBASE=/usr/gcc/7).

■ Solaris Studio 
In order to install Solaris Studio some other dependencies need to be
satisfied:

pkg:/system/library/c++-runtime
pkg:/system/library/libv12n
pkg:/system/library/mmheap
pkg:/system/library/openmp
pkg:/library/c++/stdcxx
pkg:/developer/library/xprofile
pkg:/developer/base-developer-utilities

Then, providing I downloaded my personal key and certificate files
from <pkg-register.oracle.com> and stored them inside /var/ssl, the
solarisstudio repository can be added with: 

$ pkg set-publisher \
    -k /var/pkg/ssl/pkg.oracle.com.key.pem \
    -c /var/pkg/ssl/pkg.oracle.com.certificate.pem \
    -G '*' -g https://pkg.oracle.com/solarisstudio/release solarisstudio

As of the time of writing this, the repo offers versions 12.[4-6] of Solaris
Studio. Version 12.6 is the only to support the C++14 language standard.

The IPS package for Studio 12.6 can be installed with:

$ pkg install --accept developerstudio-126

This will install the whole toolchain, along with the
observability tools, dbx, the distributed make and the NetBeans-based
studio IDE. If you want to choose individual packages, have a look at:

$ pkg list -af 'pkg://solarisstudio/developer/developerstudio-126/*'

Finally it should be checked that also the following packages are
installed: 

pkg:/consolidation/sunpro/sunpro-incorporation
pkg:/group/feature/developer-studio-utilities
pkg:/system/library/studio-runtime

The entire suite can be found at /opt/developerstudio12.6. Should be
appended to the standard user's PATH. 

■ bootstrapping with Solaris Studio 
Since pkgsrc by default searches for Solaris Studio in /opt/SUNWspro
whenever the compiler is set to sunpro, SUNWPROBASE needs to be declared.

Assuming pkgsrc was extracted to /opt/pkgsrc and that /opt/pkg is the
preferred PREFIX to use, pkgsrc can be bootstrapped with:

env CC=/opt/developerstudio12.6/bin/cc \
	SUNWSPROBASE=/opt/developerstudio12.6 \
	PKGSRC_COMPILER=sunpro \
	./bootstrap --abi=64 --prefix /opt/pkg

A mk.conf will be generated inside inside $PREFIX/etc, to store the
settings relative to compiler and destdirs.

■ additional notes
I added some more tweaks which can prove useful on SunOS systems:
(at the very least PREFER.xorgproto=pkgsrc should be set, or libXfixes
will fail to build)

.ifdef BSD_PKG_MK	# begin pkgsrc settings

ABI=				64
CC=				cc
CXX=				CC
CPP=				cc -E
CXXCPP=				CC -E
CFLAGS+=			-fast -xarch=sse3a -xopenmp=parallel
PKGSRC_COMPILER=		sunpro
SUNWSPROBASE=			/opt/developerstudio12.6

_OPSYS_SUPPORTS_SSP=		no
PKG_DBDIR=			/opt/pkg/pkgdb
LOCALBASE=			/opt/pkg
SYSCONFBASE=			/opt/pkg/etc
VARBASE=			/opt/pkg/var
PKG_TOOLS_BIN=			/opt/pkg/sbin
PKGINFODIR=			info
PKGMANDIR=			man

PREFER_PKGSRC=			yes
PREFER_NATIVE?=			oracle-jre8 zlib bzip2 motif
JAVA_BINPREFIX=			/usr/bin
PKG_DEFAULT_OPTIONS=		dtrace unicode
PREFER_NATIVE_PTHREADS=		yes

TOOLS_PLATFORM.install=		/opt/local/bin/bsdinstall
TOOLS_PLATFORM.awk=		/opt/local/bin/nawk
TOOLS_PLATFORM.sed=		/opt/local/bin/nbsed
TOOLS_PLATFORM.sh=		/usr/bin/bash

PKG_OPTIONS.fvwm3=		-svg 

.endif			# end pkgsrc settings

At this point all that's left to do is adding $PREFIX/{bin,sbin} to
PATH and $PREFIX/man to MANPATH. The runtime linking enviroment for
64-bit objects whould be reconfigured accordingly, so as to include
$PREFIX/lib. For example:

$ crle -64 -c /var/ld/64/ld.config -l /lib/64:/usr/lib/64:/opt/pkg/lib

Always take into account that on Solaris any LD_LIBRARY_PATH is
prepended to the list of directories stored in the crle database.

Realistically, regardless of the compiler used during the bootstrap
process, it is good practicw to fall back to a standard GCC version
provided by pkgsrc. This can be done by adding: 

USE_PKGSRC_GCC=YES

to $PREFIX/mk.conf. This will make pkgsrc include lang/gcc* among build  
dependencies and compile it with Solaris Studio before attempting to build
any more packages.  The internal version of the GNU Compiler will be
used as preferred compiler from this moment on. The desired GCC version
to use can be forced by specifying GCC_REQD in mk.conf.    

At this point any former compiler setting should be commented. If
libtool-base was compiled before switching compiler, it should be
rebuilt in order to prevent libtool from complaining about missing
'--tag=CC' flags while building packages.