We were seeing a ton of empty perl modules being created such as
"perl-module-x86-64-linux-encoding" where the name would include
${TARGET_ARCH}-linux. These files were already being filtered in an
earlier do_split_packages() expression so exclude them from the latter
one to remove the pointless empty modules in PACKAGES.
This doesn't explain why some were not deterministic but will recude
the do_package execution time and clean up the build directories
at the very least.
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>