bazel uses gcc's -MF option to write dependencies to a
file. Post-compilation, bazel reads this file and makes some
determinations.
"Since gcc is given only relative paths on the command line,
non-system include paths here should never be absolute. If they
are, it's probably due to a non-hermetic #include, & we should stop
the build with an error."
Spack directly injects absolute paths, which appear in this file and
cause bazel to fail the build despite the fact that compilation
succeeded.
This patch disables this failure mode by default, and allows for it
to be turned back on by using the '~nodepfail' variant.
67b86623a2