Add 2 SDK directories that can build under Cygwin/Mingw

Change-Id: I020c2691d7d92a48bd406360e2752357ae79e3b0
diff --git a/core/main.mk b/core/main.mk
index 97d3d7e..145a3f5 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -395,6 +395,7 @@
 
 subdirs := \
 	prebuilt \
+	prebuilts \
 	build/libs/host \
 	build/tools/zipalign \
 	dalvik/dexdump \
@@ -441,6 +442,7 @@
 	sdk/ide_common \
 	sdk/jarutils \
 	sdk/layoutlib_api \
+	sdk/manifmerger \
 	sdk/ninepatch \
 	sdk/rule_api \
 	sdk/lint \