Re-organize the SDK, moving the build tools out of the platforms.

Change-Id: I4526310a1c882ad33084d94e118b1c74b3181a6a
diff --git a/sdk/plat_tools_source.properties b/sdk/plat_tools_source.properties
new file mode 100644
index 0000000..ba79b6c
--- /dev/null
+++ b/sdk/plat_tools_source.properties
@@ -0,0 +1,2 @@
+Pkg.UserSrc=false
+Pkg.Revision=1