Match Rust gcda output to cc via -Z profile-emit.

Use the -Z profile-emit flag to ensure that rust gcda files have
/proc/self/cwd/ appended to them similar to cc modules. This makes sure
our gcda output is consistent no matter what language the binary is
written in.

Bug: 156482307
Test: gcda outputs to the new path.

Change-Id: Ife4d55f885c7e33dffa66f7436bc2bf8b5916586