Do not call _exit() for PGO instrumentation

Bug: http://b/63768402

For PGO instrumentation, the profiles are written by an atexit callback.
Exit normally and do not call _exit()  when PGO instrumentation is
hinted with the ANDROID_PGO_INSTRUMENTATION build flag.

Test: Build and verify that the atexit() callbcak is invoked during PGO
instrumentation.

Change-Id: I5024d965627392aee5a04e106946bb47ca48b5d6
2 files changed