OpenMP: Correctly query location for amdgpu-arch

This was trying to figure out the build path for amdgpu-arch, and
making assumptions about where it is which were not working on my
system. Whether a standalone build or not, we should have a proper
imported target to get the location from.

GitOrigin-RevId: 935abeaace123e5f11792a5175079d974d0a0be8
1 file changed