Filter -fno-delete-null-pointer-checks for clang

Fixes Homebrew/homebrew#27836.

Library/ENV/4.3/cc

@@ -121,7 +121,7 @@ class Cmd
            '-pedantic', '-pedantic-errors'
       when '-fopenmp', '-lgomp', '-mno-fused-madd', '-fforce-addr', '-fno-defer-pop',
            '-mno-dynamic-no-pic', '-fearly-inlining', '-finline-functions-called-once',
-           /^-finline-limit/,  /^-f(?:no-)?check-new/
+           /^-finline-limit/, /^-f(?:no-)?check-new/, '-fno-delete-null-pointer-checks'
         # clang doesn't support these flags
         args << arg if not tool =~ /^clang/
       when /^-W.*/