Separate out PGO profile files per arch

Bug: http://b/78259283

Specify separate PGO profiles for AArch64/ARM and x86_64/x86.  This
allows per-arch profile collection that exercises ART's code generation
for the corresponding 32-bit and 64-bit ABIs.

Test: Build Sailfish and x86_64 targets and verify that corresponding
profile files are read.

Change-Id: Iad3a657411676952de5ed446db4dd4e754ea9e11