Use general hardening flag toggle lists

The following parameters are now available:

  * hardeningDisable
    To disable specific hardening flags
  * hardeningEnable
    To enable specific hardening flags

Only the cc-wrapper supports this right now, but these may be reused by
other wrappers, builders or setup hooks.

cc-wrapper supports the following flags:

  * fortify
  * stackprotector
  * pie (disabled by default)
  * pic
  * strictoverflow
  * format
  * relro
  * bindnow

pkgs/tools/networking/uwimap/default.nix

@@ -14,7 +14,7 @@ stdenv.mkDerivation {
     # -fPIC is required to compile php with imap on x86_64 systems
     + stdenv.lib.optionalString stdenv.isx86_64 " EXTRACFLAGS=-fPIC";
 
-  hardening_format = false;
+  hardeningDisable = [ "format" ];
 
   buildInputs = [ openssl ]
     ++ stdenv.lib.optional (!stdenv.isDarwin) pam;