system/core/include is included in the global include path using
-isystem, which hides all warnings. cutils/trace.h has an ignored
return value warning, move the implementation to trace-dev.c so it
doesn't cause warnings in every module that includes it in preparation
for moving from -isystem to -I.
Test: m -j native
Bug: 31492149
Change-Id: If8b3fe13059c9e59c2d5208294d427d84fa6e588
This change defines atrace_* functions for the host that act as
no-ops, which makes it easier to add tracing in ART.
Change-Id: I89397e83986686a2b6a6f245c25017eb379081b1