This method accepts a single function that takes no arguments and
returns a single value which can be a value that can be cast to
a 64-bit signed integer, or a string, and returns that value.
Mostly useful for running foolib_version() functions that return the
currently-available version of libraries.
CCache requires this flag when building with precompiled headers.
Without it, the preprocessor fails and CCache fallbacks to running the
real compiler.
Users still need to set 'sloppiness' to 'pch_defines,time_macros' in
their ccache.conf file for CCache to cache builds that use precompiled
headers. See the CCache manual for more info:
https://ccache.samba.org/manual.html#_precompiled_headers
In addition to filtering libs out while generating the command-line, we
must also filter them out in find_library() otherwise these libs will be
detected as "found" on Windows with MSVC.
Closes https://github.com/mesonbuild/meson/issues/1509