perf: lift TARGET_CC_ARCH modification out of security_flags.inc

Building perf without security_flags.inc being included in one's
distro results in the buildpaths warning

WARNING: perf-1.0-r9 do_package_qa: QA Issue: File /usr/bin/trace in
package perf contains reference to TMPDIR

because the ${DEBUG_PREFIX_MAP} does not get used. Most recipes get
that from CFLAGS, but the perf recipe explicitly unsets that.

Now ${SELECTED_OPTIMIZATION} of course contains more than just
${DEBUG_FLAGS}/${DEBUG_PREFIX_MAP}. For most TUs, perf's build system
adds its own optimization flags (-O6 for odd reasons), so for those
including the -O2 or -Og doesn't change anything. But looking at the
.o.cmd files show that there are some TUs which currently get built
without any -O flag. So for those adding the distro's
SELECTED_OPTIMIZATION seem to be the right thing to do.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>