iterm2: fix build

During iterm2's build, xcodebuild invokes $LD and passes it options such
as -isysroot. These options are intended for the linker driver (clang),
not for the linker directly. ld64 ($LD) does not recognize these
options, causing iterm2's build to fail.

Set $LD to $CC (clang) as intended, making iterm2's build succeed.

pkgs/applications/misc/iterm2/default.nix

@@ -15,6 +15,7 @@ stdenv.mkDerivation rec {
   postPatch = ''
     sed -i -e 's/CODE_SIGN_IDENTITY = "Developer ID Application"/CODE_SIGN_IDENTITY = ""/g' ./iTerm2.xcodeproj/project.pbxproj
   '';
+  preConfigure = "LD=$CC";
   makeFlagsArray = ["Deployment"];
   installPhase = ''
     mkdir -p "$out/Applications"