defaultGemConfig.grpc: Fix build on v1.48.0+

Upstream commit 0a5d9828c1f6b32e8462a00029b1ba2a720c867b changed how the
extension build script detects an Apple toolchain; adjust accordingly by
forcing it to be false. Keep both fixes so this is more compatible.

pkgs/development/ruby-modules/gem-config/default.nix

@@ -321,8 +321,12 @@ in
       substituteInPlace Makefile \
         --replace '-Wno-invalid-source-encoding' ""
     '' + lib.optionalString stdenv.isDarwin ''
+      # For < v1.48.0
       substituteInPlace src/ruby/ext/grpc/extconf.rb \
         --replace "ENV['AR'] = 'libtool -o' if RUBY_PLATFORM =~ /darwin/" ""
+      # For >= v1.48.0
+      substituteInPlace src/ruby/ext/grpc/extconf.rb \
+        --replace 'apple_toolchain = ' 'apple_toolchain = false && '
     '';
   };