Gcc versions before 4.4 do not recognize the __optimize__ compiler
attribute:

    warning: ‘__optimize__’ attribute directive ignored

Fixes: 7375ae3a ("compiler-gcc.h: Introduce __nostackprotector function attribute")
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>