cc-wrapper: set gl_cv_clean_version_stddef=yes on cygwin (#468206)

pkgs/build-support/cc-wrapper/default.nix

@@ -603,6 +603,10 @@ stdenvNoCC.mkDerivation {
         if targetPlatform.isCygwin then
           ''
             echo addToSearchPath "LINK_DLL_FOLDERS" "${cc_bin}/lib" >> $out
+            # Work around build failure caused by the gnulib workaround for
+            # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114870. remove after
+            # gnulib is updated in core packages (e.g. iconv, gnupatch, gnugrep)
+            echo appendToVar configureFlags gl_cv_clean_version_stddef=yes >> $out
           ''
         else
           ''

pkgs/development/libraries/libidn2/default.nix

@@ -44,12 +44,6 @@ stdenv.mkDerivation rec {
   buildInputs = [ libunistring ] ++ lib.optional stdenv.hostPlatform.isDarwin libiconv;
   depsBuildBuild = [ buildPackages.stdenv.cc ];
 
-  configureFlags =
-    # Work around build failure caused by the gnulib workaround for
-    # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114870.
-    # remove after gnulib is updated
-    lib.optional stdenv.hostPlatform.isCygwin "gl_cv_clean_version_stddef=yes";
-
   meta = {
     homepage = "https://www.gnu.org/software/libidn/#libidn2";
     description = "Free software implementation of IDNA2008 and TR46";

pkgs/tools/text/gnugrep/default.nix

@@ -80,11 +80,6 @@ stdenv.mkDerivation {
     export MKDIR_P="mkdir -p"
   '';
 
-  configureFlags =
-    # Work around build failure caused by the gnulib workaround for
-    # https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114870. remove after GCC 15
-    lib.optional stdenv.hostPlatform.isCygwin "gl_cv_clean_version_stddef=yes";
-
   enableParallelBuilding = true;
 
   # Fix reference to sh in bootstrap-tools, and invoke grep via