It's fairly common on Linux and *BSD platforms to check for these
attributes existence, so it makes sense to me to have this checking
build into meson itself. Autotools also has a builtin for handling
these, and by building them in we can short circuit cases that we know
that these don't exist (MSVC).
Additionally this adds support for two common MSVC __declspec
attributes, dllimport and dllexport. This implements the declspec
version (even though GCC has an __attribute__ version that both it and
clang support), since GCC and Clang support the MSVC version as well.
Thus it seems reasonable to assume that most projects will use the
__declspec version over teh __attribute__ version.
Instead of exposing the endianness in the CPU family, canonicalise the CPU
family to just "ppc64" to match MIPS (which is also bi-endian).
Part of the work for #3842.
* environment: validate cpu_family in cross file
* run_unittests: add unittest to ensure CPU family list in docs and environment matches
* run_unittests: skip compiler options test if not in a git repository
* environment: validate the detected cpu_family
* docs: add 32-bit PowerPC and 32/64-bit MIPS to CPU Families table
Names gathered by booting Linux in Qemu and running:
$ python3
import platform; platform.machine()
Partial fix for #3751