Fix a Windows-only discrepency in the Windows SDK build.

For some reason, there's a slight behavior difference between
my Windowss machine and the Windows build servers, that is on
mine the include of framework/base results in duplicate build
rules being defined. My machine used to work like the Windows
build server and the behavior mysteriously changed a while
ago. This change should make it all work the same on all boxes.

Change-Id: I45e02e9eadfc586f86caa6a2690deda9648e600d
diff --git a/core/main.mk b/core/main.mk
index 9dd6888..ffbafe2 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -392,7 +392,6 @@
 	sdk/layoutopt \
 	development/apps \
 	development/tools/mkstubs \
-	frameworks/base \
 	frameworks/base/tools/layoutlib \
 	external/googleclient \
 	packages