Revert "llvmPackages_11: Add $rsrc/lib to default cflags"

This reverts commit 2000ae5429.

This was intended as a fix for i686 cross compilation, but it has had
other unforeseen consequences, such as breaking rust-bindgen.

pkgs/development/compilers/llvm/11/default.nix

@@ -43,7 +43,6 @@ let
       mkdir "$rsrc"
       ln -s "${cc.lib}/lib/clang/${release_version}/include" "$rsrc"
       echo "-resource-dir=$rsrc" >> $out/nix-support/cc-cflags
-      echo "-B $rsrc/lib" >> $out/nix-support/cc-cflags
     '';
     mkExtraBuildCommands = cc: mkExtraBuildCommands0 cc + ''
       ln -s "${targetLlvmLibraries.compiler-rt.out}/lib" "$rsrc/lib"