Header files are built immediately, not in a separate job, so no
dependency is needed here. All we need is a flag whether to add flags
for that given libc.
A few small changes were needed to make this work. In particular, I
found a critical bug (see the previous commit) that needed to be fixed
to make this work on Windows.
This adds support for the well-known Boehm GC. It's significantly faster
than our own naive GC and could be used as an alternative on bigger
systems.
In the future, this GC might also be supported on WebAssembly with some
extra work. Right now it's Linux only (though Windows/MacOS shouldn't be
too difficult to add).
Ayke van Laethem