-CFLAGS += $(call cc-option,-funsigned-char -static-libgcc,)
-CFLAGS += $(call cc-option,-falign-functions=1 -falign-jumps=1 -falign-labels=1 -falign-loops=1,)
+CFLAGS += $(call cc-option,-funsigned-char,)
+
+ifneq ($(CC),clang)
+# "clang-9: warning: argument unused during compilation: '-static-libgcc'"
+CFLAGS += $(call cc-option,-static-libgcc,)
+endif
+
+CFLAGS += $(call cc-option,-falign-functions=1,)
+ifneq ($(CC),clang)
+# "clang-9: warning: optimization flag '-falign-jumps=1' is not supported" (and same for other two)
+CFLAGS += $(call cc-option,-falign-jumps=1 -falign-labels=1 -falign-loops=1,)
+endif
+