stdcxx: do not pass -stdlib=libc++ to the linker

pkgs/stdcxx/default.nix

@@ -18,8 +18,8 @@ in stdenv.mkDerivation rec {
   dontBuild = true;
 
   installPhase = ''
-    cflags=$NIX_CXXSTDLIB_COMPILE libs=$NIX_CXXSTDLIB_LINK \
-    	substituteAll ${./stdcxx.pc} ${pname}.pc
+    cflags=$NIX_CXXSTDLIB_COMPILE \
+      substituteAll ${./stdcxx.pc} ${pname}.pc
     mkdir -p $out/lib/pkgconfig
     install -Dm444 *.pc $out/lib/pkgconfig
   '';

pkgs/stdcxx/stdcxx.pc

@@ -3,4 +3,3 @@ Description: Genode Standard C++ library
 Version: @version@
 Requires: libc libm
 Cflags:  @cflags@
-Libs: @libs@