Add support for software performance analysis (will likely vary from ebuild to ebuild)

Packages describing “profile” as local USE flag

Package“profile” Flag Description
app-portage/hackportEnable profiling flags
games-rpg/freedroidrpgEnable the integration of the ingame real-time profiler
sys-libs/compiler-rt-sanitizersBuild profiling runtime.

All packages providing a “profile” USE flag (527)