Revert "Fix DEBUG=1 builds"

This reverts commit 6e76f7bc90fcd130db888f8804b8555dc8f3a484.

This patch tries to workaround a previous clang workaround. Instead of going
into workaround of workaround spiral, the original workaround should be tamed.
unix/gccollect.c: Make Clang workaround apply only to it. Unbreaks gcc builds.