silence compiler warnings for macOS

After silencing compiler warnings for RHEL 9 Linux,
we silence the result on macOS for
Apple clang version 15.0.0 (clang-1500.3.9.4).

1984/anonymous/Makefile

@@ -41,7 +41,8 @@ include ../../var.mk
 CSILENCE= -Wno-error -Wno-implicit-function-declaration -Wno-implicit-int \
 	  -Wno-return-type -Wno-string-plus-int -Wno-unsequenced \
 	  -Wno-deprecated-non-prototype -Wno-void-pointer-to-int-cast \
-	  -Wno-missing-parameter-type -Wno-pointer-to-int-cast
+	  -Wno-missing-parameter-type -Wno-pointer-to-int-cast \
+	  -Wno-unknown-warning-option
 
 # Common C compiler warning flags
 #