Log Message:
Only add -lgcc_s explicitly on NetBSD 5. Disable parallel GC in
rules.make and explicitly on calls to ant. Be nice and raise the memory
limit to 1G. Adjust ant rules to also apply SerialGC + 1G limit.

This currently reverts to the default settings for !BSD, if necessary
the changes to rules.make should be copied.

Add a small fragment for providing lang/openjdk7/libs with compat
versions of libstdc++ and libgcc_s to allow using the GCC bootstrap in a
pure clang release. Versions can be obtained from NetBSD 6's base.tgz.