Now that the linkers are split out of the compilers this enum is
only used to know what platform we're compiling for. Which is
what the MachineInfo class is for
To make Fortran tests useful on Windows, the library_type should default to static,
unless needed to specifically test shared. Shared Fortran libs on Windows for
non-Gfortran compilers is fragile requiring proprietary code syntax.
* PGI C++ PCH enable
PGI compilers support precompiled headers for C++ only.
The common/13 pch test passes if run manually with no spaces in the build path.
However, since Meson run_project_tests.py makes temporary build directories
with spaces in each tests, PGI --pch_dir can't handle this and fails.
So we skip the test for PGI despite it working for usual case with no-spaces
in build dir.
Note: it's fine to have spaces in full path for sourcedir, just no spaces in
relative path to builddir.
* doc