Bug#1069607: retroarch is built without optimization

[Adrian Bunk]

Package: retroarch
Version: 1.18.0+dfsg-1
Severity: important
Tags: ftbfs
X-Debbugs-Cc: Jonathan McDowell <noodles at earth.li>

debian/rules:export DEB_CXXFLAGS_MAINT_STRIP=-O2
debian/rules:export DEB_CFLAGS_MAINT_STRIP=-O2

Building without optimization makes binaries
both slower and bigger.

The latter is likely also the root cause of the FTBFS
on m68k and powerpc.