simpleperf: fix unpadding build id in pprof_proto_generator.py.

The current logic forgets to unpad build id for elf files in
binary_cache.

Bug: 208474310
Test: scripts/test/test.py --only-host-test
Change-Id: Ie1e2fc4b682afc15bd0327d01896bc40e04f75b6
3 files changed