libgcc: Add MLPREFIX to sanity check skip

libgcc: Add MLPREFIX to sanity check skip

Fixes:
ERROR: QA Issue: non -staticdev package contains static .a library: lib32-libgcov-dev path '/work/x86-pokymllib32-linux/lib32-libgcc-4.7.0+svnr186651-r0/packages-split/lib32-libgcov-dev/usr/lib/i586-pokymllib32-linux/4.7.1/libgcov.a'
ERROR: QA run found fatal errors. Please consider fixing them.
ERROR: Function failed: do_package_qa
ERROR: Logfile of failure stored in: /srv/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-multilib/build/build/tmp/work/x86-pokymllib32-linux/lib32-libgcc-4.7.0+svnr186651-r0/temp/log.do_package.9691
NOTE: package lib32-libgcc-4.7.0+svnr186651-r0: task do_package: Failed
ERROR: Task 1077 (virtual:multilib:lib32:/srv/home/pokybuild/yocto-autobuilder/yocto-slave/nightly-multilib/build/meta/recipes-devtools/gcc/libgcc_4.7.bb, do_package) failed with exit code '1'
Signed-off-by: Saul Wold <sgw@linux.intel.com>