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.
I recall that @jpakkane never wanted this, but @nirbheek did, but then
@nirbheek changed his mind.
I am fine either way except for the cross inconsistency that exists
today: There is no `c_preproc_args` or similar one can put in the cross
file, so no way to replicate the effect of CPPFLAGS during cross
compilation.
This adds a hidden option to dump the current otherwise hidden peristant
state in coredata.dat.
This interface is unstable as meson has no compatibility promises about
coredata.dat.