EmulatorPkg/Unix/Host: Fix XCODE5 IA32/X64 build failure

EmulatorPkg/Unix/Host: Fix XCODE5 IA32/X64 build failure

https://bugzilla.tianocore.org/show_bug.cgi?id=2046

* Clean up XCODE5 IA32 [BuildOptions] and fix IA32
  X11 include path.
* Add -DEFIAPI=__attribute__((ms_abi)) to X64 XCODE5
  [BuildOptions]
* Use -target x86_64-apple-darwin for X64 XCODE5
  [BuildOptions]
* Add Wl,-no_pie to X64 XCODE5 [BuildOptions]
* Address function type mismatch reported by XCODE5
  in reverse gasket callback between UEFI ABI and
  MacOS ABI.  Use a UINTN to pass function address
  to assembly code.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Andrew Fish <afish@apple.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>