/bootstrap/build/gcc-stage{1,2}.bst: Fix conditionals
We overrided conditionals '(?)' from build.yml instead of appending them, so the CFLAGS were not properly set.
Discovered when backporting last fix to 18.08 with !1429 (merged) (fix is there).
We overrided conditionals '(?)' from build.yml instead of appending them, so the CFLAGS were not properly set.
Discovered when backporting last fix to 18.08 with !1429 (merged) (fix is there).