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
In most cases instead pass `for_machine`, the name of the relevant
machines (what compilers target, what targets run on, etc). This allows
us to use the cross code path in the native case, deduplicating the
code.
As one can see, environment got bigger as more information is kept
structured there, while ninjabackend got a smaller. Overall a few amount
of lines were added, but the hope is what's added is a lot simpler than
what's removed.
Previously cross, but not native, external args were used. Then in
d451a4bd97 the cross special cases were
removed, so external args are never used.
This commit switches that so they are always used. Sanity checking works
just the same as compiler checks like has header / has library.
Fixes "warning: --output and -o have no effect when -C or --ccode is set"
get_always_args() adds -C which is already disabling the direct compilation
ability of valac for which -o is used.
As the Vala compiler does not define thread_flags() and
thread_link_flags(), depending on threads in any capacity will cause Meson to
fail.
Fixes#2720.