The rust language supports $RUSTFLAGS to be used automatically in all
rustc invocations. Allow setting this in makepkg.conf (e.g. for
optimization or debuginfo support), and teach debug+strip to pass the
rustc command line argument necessary to rewrite source file paths in
the debugging symbols.
Signed-off-by: Eli Schwartz <eschwartz@archlinux.org>
Signed-off-by: Allan McRae <allan@archlinux.org>