Skip test earlier if metric is not found in compare.py

This speeds up processing for inputs with lots of missing metrics, by
avoiding adding them to names.

Reviewed By: paquette

Differential Revision: https://reviews.llvm.org/D64065


git-svn-id: https://llvm.org/svn/llvm-project/test-suite/trunk@366999 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed