glibc: add support for C.utf-8

pkgs/development/libraries/glibc/common.nix

@@ -87,6 +87,11 @@ stdenv.mkDerivation ({
         less linux-*?/arch/x86/kernel/syscall_table_32.S
        */
       ./allow-kernel-2.6.32.patch
+      /* Provide utf-8 locales by default, so we can use it in stdenv without depending on our large locale-archive. */
+      (fetchurl {
+        url = "https://salsa.debian.org/glibc-team/glibc/raw/49767c9f7de4828220b691b29de0baf60d8a54ec/debian/patches/localedata/locale-C.diff";
+        sha256 = "0irj60hs2i91ilwg5w7sqrxb695c93xg0ik7yhhq9irprd7fidn4";
+      })
     ]
     ++ lib.optional stdenv.isx86_64 ./fix-x64-abi.patch
     ++ lib.optional stdenv.hostPlatform.isMusl ./fix-rpc-types-musl-conflicts.patch;

pkgs/development/libraries/glibc/default.nix

@@ -56,9 +56,8 @@ callPackage ./common.nix { inherit stdenv; } {
     '';
 
     postInstall = ''
-      if test -n "$installLocales"; then
-          make -j''${NIX_BUILD_CORES:-1} -l''${NIX_BUILD_CORES:-1} localedata/install-locales
-      fi
+      echo SUPPORTED-LOCALES=C.UTF-8/UTF-8 > ../glibc-2*/localedata/SUPPORTED
+      make -j''${NIX_BUILD_CORES:-1} -l''${NIX_BUILD_CORES:-1} localedata/install-locales
 
       test -f $out/etc/ld.so.cache && rm $out/etc/ld.so.cache