Always generate profiling debug info

The additional debug info is used for sampling PGO. This does not affect
the size of final stripped binaries.

Also removed `-gmlt` flag in pgo.go, since it's actually a lower level
of debug option than the default (-g).

Test: build, verify final binaries are identical size
Bug: 79161490
Change-Id: Ie4cf4998695f78a50a7ac7a7a0853c625cbd8880