ccls: fix libc++ header path

(cherry picked from commit eef236e8efdf99e4e4d61815aa9889e5b64e6bc3)

pkgs/development/tools/misc/ccls/default.nix

@@ -21,17 +21,11 @@ stdenv.mkDerivation rec {
     cmakeFlagsArray+=(-DCMAKE_CXX_FLAGS="-fvisibility=hidden -fno-rtti")
   '';
 
+  clang = llvmPackages.clang;
   shell = runtimeShell;
+
   postFixup = ''
-    # We need to tell ccls where to find the standard library headers.
-
-    standard_library_includes="\\\"-isystem\\\", \\\"${lib.getDev stdenv.cc.libc}/include\\\""
-    standard_library_includes+=", \\\"-isystem\\\", \\\"${llvmPackages.libcxx}/include/c++/v1\\\""
-    export standard_library_includes
-
-    wrapped=".ccls-wrapped"
-    export wrapped
-
+    export wrapped=".ccls-wrapped"
     mv $out/bin/ccls $out/bin/$wrapped
     substituteAll ${./wrapper} $out/bin/ccls
     chmod --reference=$out/bin/$wrapped $out/bin/ccls