Add x86_64-darwin10-gcc target.

Adds native build configuration for Snow Leopard.  Useful when
users configure without arguments on OSX 10.6.

Change-Id: I0bd63912a25bbfb9d4c8d58a781d0f390792429c

build/make/configure.sh

@@ -547,6 +547,10 @@ process_common_toolchain() {
                 tgt_isa=universal
                 tgt_os=darwin9
                 ;;
+            *darwin10*)
+                tgt_isa=x86_64
+                tgt_os=darwin10
+                ;;
             *mingw32*|*cygwin*)
                 [ -z "$tgt_isa" ] && tgt_isa=x86
                 tgt_os=win32
@@ -606,6 +610,12 @@ process_common_toolchain() {
             add_ldflags "-isysroot /Developer/SDKs/MacOSX10.5.sdk"
             add_ldflags "-mmacosx-version-min=10.5"
             ;;
+        *-darwin10-*)
+            add_cflags  "-isysroot /Developer/SDKs/MacOSX10.6.sdk"
+            add_cflags  "-mmacosx-version-min=10.6"
+            add_ldflags "-isysroot /Developer/SDKs/MacOSX10.6.sdk"
+            add_ldflags "-mmacosx-version-min=10.6"
+            ;;
     esac
 
     # Handle Solaris variants. Solaris 10 needs -lposix4

configure

@@ -115,6 +115,7 @@ all_platforms="${all_platforms} x86-win32-vs7"
 all_platforms="${all_platforms} x86-win32-vs8"
 all_platforms="${all_platforms} x86-win32-vs9"
 all_platforms="${all_platforms} x86_64-darwin9-gcc"
+all_platforms="${all_platforms} x86_64-darwin10-gcc"
 all_platforms="${all_platforms} x86_64-linux-gcc"
 all_platforms="${all_platforms} x86_64-linux-icc"
 all_platforms="${all_platforms} x86_64-solaris-gcc"