--- lib/freebl/Makefile~
+++ lib/freebl/Makefile
@@ -659,7 +659,7 @@ $(OBJDIR)/$(PROG_PREFIX)intel-gcm-wrap$(
 # symbolic names to registers, for example,
 #     .set  Htbl, %rdi
 # So we can't use Clang's integrated assembler with intel-gcm.s.
-ifneq (,$(findstring clang,$(AS)))
+ifneq (,$(findstring clang,$(shell $(AS) -v 2>&1)))
 $(OBJDIR)/$(PROG_PREFIX)intel-gcm$(OBJ_SUFFIX): ASFLAGS += -no-integrated-as
 endif
 endif