Clang supported header searchpaths of the form `-I =/path`, relative to
the sysroot if one is passed, but did not implement that behavior for
`-iquote`, `-isystem`, or `-idirafter`.
This implements the `=` portion of the behavior implemented by GCC for
these flags described in
https://gcc.gnu.org/onlinedocs/gcc/Directory-Options.html.
Replace use of /dev/null with /var/empty. lit will substitute the /dev/null
include path resulting in failures. Use a path under /var/empty which is
supposed to be empty to ensure that we can successfully test.
llvm-svn: 268784
From the GCC manpage:
-I dir
... If dir begins with =, then the = will be replaced by the sysroot prefix;
see --sysroot and -isysroot.
Add support to expand the `=` as a prefix of the include path with the sysroot
if specified. `-isysroot` takes precedence over `--sysroot` as the normal
argument behaviour occurs. The ordering of the `-isysroot` is relevant to the
path substituted. If no `--sysroot=` or `-isysroot` option is present, the = is
not expanded.
Resolves PR26965!
llvm-svn: 268777
