perf: Use python3targetconfig to ensure we use target libraries

We've seen some reproducibility issues on the autobuilder in perf where the
size of the python module varies slightly between systems. After some head
scratching and removing the --quiet option to the python module build,
you can see it using -Lrecipe-sysroot-native in the linking commandline
for the module. This means it is linking against the native library
on systems where that works, skipping it and using the target one
otherwise, probably with warnings in logs we've not seen.

The fix is to inherit the python3targetconfig class which ensures
that the target sysroot is used, then the byte differences between
the builds go away and things are sane(r) again.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>