Use glibc-2.27 for RISC-V support.

pkgs/top-level/all-packages.nix

@@ -8763,7 +8763,11 @@ with pkgs;
   };
 
   # Being redundant to avoid cycles on boot. TODO: find a better way
-  glibcCross = callPackage ../development/libraries/glibc {
+  glibcCross = let
+    expr = if hostPlatform.isRiscV
+             then ../development/libraries/glibc/2.27.nix
+           else ../development/libraries/glibc;
+  in callPackage expr {
     installLocales = config.glibc.locales or false;
     stdenv = crossLibcStdenv;
   };