Update Makefile so LTO works on OSX

The gold linker can only produce ELF binaries, not Mach, so it doesn't work on OSX. This lets link-time optimization work when linking Mach binaries from clang.

Makefile

@@ -185,7 +185,8 @@ ifeq ($(RUNTESTS), 1)
   TESTS = tests
 endif
 
-# tiles object directories are because gcc gets confused # Appears that the default value of $LD is unsuitable on most systems
+# tiles object directories are because gcc gets confused
+# Appears that the default value of $LD is unsuitable on most systems
 
 # when preprocessor defines change, but the source doesn't
 ODIR = $(BUILD_PREFIX)obj
@@ -283,6 +284,7 @@ ifdef RELEASE
       OPTLEVEL = -Os
     endif
   endif
+
   ifdef LTO
     ifdef CLANG
       # LLVM's LTO will complain if the optimization level isn't between O0 and
@@ -293,7 +295,14 @@ ifdef RELEASE
   CXXFLAGS += $(OPTLEVEL)
 
   ifdef LTO
-    LDFLAGS += -fuse-ld=gold
+    ifeq ($(NATIVE), osx)
+      ifdef CLANG
+        LTOFLAGS += -flto=full
+      endif
+    else
+      LDFLAGS += -fuse-ld=gold # This breaks in OS X because gold can only produce ELF binaries, not Mach
+    endif
+
     ifdef CLANG
       LTOFLAGS += -flto
     else
@@ -303,6 +312,8 @@ ifdef RELEASE
   CXXFLAGS += $(LTOFLAGS)
 
   # OTHERS += -mmmx -m3dnow -msse -msse2 -msse3 -mfpmath=sse -mtune=native
+  # OTHERS += -march=native # Uncomment this to build an optimized binary for your machine only
+
   # Strip symbols, generates smaller executable.
   OTHERS += $(RELEASE_FLAGS)
   DEBUG =