RPI-B cmake "Cannot find a C++ compiler that supports both C++11 and the specified C++ flags"

[John Kennedy]

On Sun, Sep 15, 2019 at 10:17:24PM +1000, Scott wrote:
> as per the thread title, I cannot compile cmake on FreeBSD 12.1-PRERELEASE
> r351916 RPI-B arm.
>
> I'm trying to compile graphics/sane-backends which of course requires cmake.
>
> Is anyone aware of a workaround?

  I've got it self-compiled on a RPI 3B+.

	FreeBSD 12.1-PRERELEASE #38 r351916+b4b21edc54b2(stable/12): Sun Sep  8 10:19:16 PDT 2019

  On my setup, looks like it's using the stock "cc" or "c++" compiler (based on MAKE_ENV from poudriere)::

	$ cc --version
	FreeBSD clang version 8.0.1 (tags/RELEASE_801/final 366581) (based on LLVM 8.0.1)
	Target: aarch64-unknown-freebsd12.1
	Thread model: posix
	InstalledDir: /usr/bin

	$ c++ --version
	FreeBSD clang version 8.0.1 (tags/RELEASE_801/final 366581) (based on LLVM 8.0.1)
	Target: aarch64-unknown-freebsd12.1
	Thread model: posix
	InstalledDir: /usr/bin

  Snip of poudriere logs:

	=>> Building devel/cmake
	build started at Wed Sep 11 17:24:15 PDT 2019
	port directory: /usr/ports/devel/cmake
	package name: cmake-3.15.3
	building for: FreeBSD 12-1-pre-master-job-01 12.1-PRERELEASE FreeBSD 12.1-PRERELEASE 1200516 arm64
	maintained by: kde at FreeBSD.org
	Makefile ident: 
	Poudriere version: 3.3.2_1
	Host OSVERSION: 1200516
	Jail OSVERSION: 1200516
	Job Id: 01
	...
	--CONFIGURE_ENV--
	MAKE=make PYTHON="/usr/local/bin/python3.6" XDG_DATA_HOME=/wrkdirs/usr/ports/devel/cmake/work  XDG_CONFIG_HOME=/wrkdirs/usr/ports/devel/cmake/work  HOME=/wrkdirs/usr/ports/devel/cmake/work TMPDIR="/tmp" PATH=/wrkdirs/usr/ports/devel/cmake/work/.bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:/root/bin SHELL=/bin/sh CONFIG_SHELL=/bin/sh CMAKE_PREFIX_PATH="/usr/local"
	--End CONFIGURE_ENV--

	--MAKE_ENV--
	XDG_DATA_HOME=/wrkdirs/usr/ports/devel/cmake/work  XDG_CONFIG_HOME=/wrkdirs/usr/ports/devel/cmake/work  HOME=/wrkdirs/usr/ports/devel/cmake/work TMPDIR="/tmp" PATH=/wrkdirs/usr/ports/devel/cmake/work/.bin:/sbin:/bin:/usr/sbin:/usr/bin:/usr/local/sbin:/usr/local/bin:/root/bin NO_PIE=yes MK_DEBUG_FILES=no MK_KERNEL_SYMBOLS=no SHELL=/bin/sh NO_LINT=YES PREFIX=/usr/local  LOCALBASE=/usr/local  CC="cc" CFLAGS="-O2 -pipe  -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing "  CPP="cpp" CPPFLAGS="-isystem /usr/local/include"  LDFLAGS=" -fstack-protector-strong " LIBS="-L/usr/local/lib"  CXX="c++" CXXFLAGS="-O2 -pipe -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing  -isystem /usr/local/include "  MANPREFIX="/usr/local" BSD_INSTALL_PROGRAM="install  -s -m 555"  BSD_INSTALL_LIB="install  -s -m 0644"  BSD_INSTALL_SCRIPT="install  -m 555"  BSD_INSTALL_DATA="install  -m 0644"  BSD_INSTALL_MAN="install  -m 444"
	--End MAKE_ENV--
	...
	=======================<phase: package        >============================
	===>  Building package for cmake-3.15.3
	===========================================================================
	=>> Cleaning up wrkdir
	===>  Cleaning for cmake-3.15.3
	build of devel/cmake | cmake-3.15.3 ended at Wed Sep 11 20:29:57 PDT 2019
	build time: 03:05:42