ovmf: Improve reproducibility by enabling prefix mapping
We want to pass ${DEBUG_PREFIX_MAP} to gcc commands and also pass in
--debug-prefix-map to nasm (we carry a patch to nasm for this). The
tools definitions are built by ovmf-native so we need to pass this in
at target build time when we know the right values.
By using determininistc file paths in the ovmf build, it removes the
opportunitity for gcc/ld to change the output binaries due to path
lengths overflowing section sizes and causing small changes in the
binary output.
This also means that if builds have reproducibility issues in future, it
becomes much easier to compare intermediate build artefacts.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
