Add x86_64 toolchains

Change-Id: I008d78b6cfa1397adccd8fd51ea0e2723fbca532
diff --git a/default.xml b/default.xml
index 46a86e6..b1bb368 100644
--- a/default.xml
+++ b/default.xml
@@ -347,6 +347,7 @@
   <project path="prebuilts/gcc/darwin-x86/mips/mipsel-linux-android-4.7" name="platform/prebuilts/gcc/darwin-x86/mips/mipsel-linux-android-4.7" groups="pdk,darwin,mips" />
   <project path="prebuilts/gcc/darwin-x86/x86/i686-linux-android-4.6" name="platform/prebuilts/gcc/darwin-x86/x86/i686-linux-android-4.6" groups="pdk,darwin,x86" />
   <project path="prebuilts/gcc/darwin-x86/x86/i686-linux-android-4.7" name="platform/prebuilts/gcc/darwin-x86/x86/i686-linux-android-4.7" groups="pdk,darwin,x86" />
+  <project path="prebuilts/gcc/darwin-x86/x86/x86_64-linux-android-4.7" name="platform/prebuilts/gcc/darwin-x86/x86/x86_64-linux-android-4.7" groups="pdk,darwin,x86" />
   <project path="prebuilts/gcc/linux-x86/arm/arm-eabi-4.6" name="platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.6" groups="pdk,linux,arm" />
   <project path="prebuilts/gcc/linux-x86/arm/arm-eabi-4.7" name="platform/prebuilts/gcc/linux-x86/arm/arm-eabi-4.7" groups="pdk,linux,arm" />
   <project path="prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.6" name="platform/prebuilts/gcc/linux-x86/arm/arm-linux-androideabi-4.6" groups="pdk,linux,arm" />
@@ -358,6 +359,7 @@
   <project path="prebuilts/gcc/linux-x86/mips/mipsel-linux-android-4.7" name="platform/prebuilts/gcc/linux-x86/mips/mipsel-linux-android-4.7" groups="pdk,linux,mips" />
   <project path="prebuilts/gcc/linux-x86/x86/i686-linux-android-4.6" name="platform/prebuilts/gcc/linux-x86/x86/i686-linux-android-4.6" groups="pdk,linux,x86" />
   <project path="prebuilts/gcc/linux-x86/x86/i686-linux-android-4.7" name="platform/prebuilts/gcc/linux-x86/x86/i686-linux-android-4.7" groups="pdk,linux,x86" />
+  <project path="prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.7" name="platform/prebuilts/gcc/linux-x86/x86/x86_64-linux-android-4.7" groups="pdk,linux,x86" />
   <project path="prebuilts/misc" name="platform/prebuilts/misc" groups="pdk" />
   <project path="prebuilts/ndk" name="platform/prebuilts/ndk" groups="pdk" />
   <project path="prebuilts/python/darwin-x86/2.7.5" name="platform/prebuilts/python/darwin-x86/2.7.5" groups="darwin" />