Check out GDB prebuilts from Android

Change-Id: I3eab1d0eca0aedaa4390ea322cf8ce9c6124088c
diff --git a/default.xml b/default.xml
index 889895f..c7ed834 100644
--- a/default.xml
+++ b/default.xml
@@ -30,4 +30,13 @@
            name="platform/prebuilts/gcc/linux-x86/aarch64/aarch64-linux-android-4.9"
            remote="aosp" revision="master"
            clone-depth="1" />
+  <project path="toolchains/darwin-x86/gdb"
+           name="platform/prebuilts/gdb/darwin-x86"
+           remote="aosp" revision="master"
+           clone-depth="1" />
+  <project path="toolchains/linux-x86/gdb"
+           name="platform/prebuilts/gdb/linux-x86"
+           remote="aosp" revision="master"
+           clone-depth="1" />
+
 </manifest>