[clang-linker-wrapper][lit] Fix OpenMP SPIR-V ELF test again (#126142)
I was able to reproduce the issue with the sanitizer buildbot scripts
and confirmed this fixes it.
The issue was the quotes, `"0"` is true in Python so we incorrectly
added the `spirv-tools` feature even when the CMake variable was false.
I don't know why it didn't always fail.
Also add the var to clang's `BUILD.gn` which matches what we do for
other similar variables, however I don't think it has any effect on CI
here.
Signed-off-by: Sarnie, Nick <nick.sarnie@intel.com>