Fix optimization of Parser.y.pp

In 9e133b, the build was modified to pass -fcmm-sink to Parser, but
unfortunately Parser specifies -O0 in its OPTIONS_GHC directive, meaning
the sinking pass was actually turned off.

HC_OPTS is the last thing passed to the compiler for that source file
however, so the correct fix is to also move -O0 out into the build
system as well.

This was uncovered thanks to a build report from Kazu Yamamoto. Thanks
to Jan Stolarek for eyeballing this bug and finding it.

Signed-off-by: Austin Seipp <aseipp@pobox.com>