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).

2006/birken/Makefile

@@ -39,7 +39,7 @@ include ../../var.mk
 # Common C compiler warnings to silence
 #
 CSILENCE= -Wno-deprecated-declarations -Wno-strict-prototypes -Wno-address \
-	  -Wno-maybe-uninitialized
+	  -Wno-maybe-uninitialized -Wno-unknown-warning-option
 
 # Common C compiler warning flags
 #

2006/hamre/Makefile

@@ -40,7 +40,8 @@ include ../../var.mk
 #
 CSILENCE= -Wno-error -Wno-implicit-function-declaration -Wno-implicit-int \
 	  -Wno-parentheses -Wno-builtin-declaration-mismatch \
-	  -Wno-misleading-indentation -Wno-unused-value
+	  -Wno-misleading-indentation -Wno-unused-value \
+	  -Wno-unknown-warning-option
 
 # Common C compiler warning flags
 #

2006/meyer/Makefile

@@ -86,7 +86,7 @@ ifeq "$(findstring $(CLANG),${CC})" "$(CLANG)"
 CSILENCE+= -Wno-missing-prototypes -Wno-missing-variable-declarations \
 	   -Wno-poison-system-directories -Wno-sign-conversion \
 	   -Wno-strict-prototypes -Wno-cast-function-type-strict \
-	   -Wno-unsafe-buffer-usage
+	   -Wno-unsafe-buffer-usage -Wno-unknown-warning-option
 #
 CWARN+= -Weverything
 #

2006/sykes1/Makefile

@@ -40,7 +40,7 @@ include ../../var.mk
 #
 CSILENCE= -Wno-bitwise-op-parentheses -Wno-shift-op-parentheses \
 	  -Wno-maybe-uninitialized -Wno-misleading-indentation -Wno-parentheses \
-          -Wno-stringop-truncation
+          -Wno-stringop-truncation -Wno-unknown-warning-option
 
 # Common C compiler warning flags
 #