Do not perform AFDO or optimizing LTO for eng builds

Afdo creates more variants to build, and optimizing LTO is costly to
perform. Turn off these two optimizations for eng builds for a faster
build speed.

This reduces total C/C++ invocation time for aosp_arm64-eng by 6.28%.

Test: presubmit
Bug: 307753064
Change-Id: Ibac4269c66a64e896dba2074b607d71a2da37546