Allow some warnings when building libgcc (#36)

Author: Blackhex

libgcc/config/aarch64/t-aarch64

@@ -30,4 +30,5 @@ LIB2ADDEH += \
 	$(srcdir)/config/aarch64/__arm_za_disable.S
 
 SHLIB_MAPFILES += $(srcdir)/config/aarch64/libgcc-sme.ver
-LIBGCC2_CFLAGS += -Werror -Wno-prio-ctor-dtor
+LIBGCC2_CFLAGS += -Werror -Wno-prio-ctor-dtor -Wno-error=attributes -Wno-error=unused-parameter \
+	-Wno-error=missing-prototypes -Wno-error=unused-function