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).

2014/birken/Makefile

@@ -41,7 +41,8 @@ include ../../var.mk
 CSILENCE= -Wno-comment -Wno-dangling-else -Wno-error \
 	  -Wno-implicit-function-declaration -Wno-incompatible-pointer-types \
 	  -Wno-parentheses -Wno-trigraphs -Wno-newline-eof \
-	  -Wno-builtin-declaration-mismatch -Wno-sequence-point
+	  -Wno-builtin-declaration-mismatch -Wno-sequence-point \
+	  -Wno-unknown-warning-option
 
 # Common C compiler warning flags
 #

2014/maffiodo1/Makefile

@@ -96,7 +96,7 @@ CSILENCE+= -Wno-comma -Wno-documentation -Wno-extra-semi -Wno-implicit-int \
 	   -Wno-declaration-after-statement -Wno-implicit-int-conversion \
 	   -Wno-extra-semi-stmt -Wno-incompatible-function-pointer-types-strict \
 	   -Wno-reserved-identifier -Wno-reserved-macro-identifier \
-	   -Wno-unsafe-buffer-usage
+	   -Wno-unsafe-buffer-usage -Wno-unknown-warning-option
 #
 CWARN+= -Weverything
 #