Add system/core to the PYTHONPATH.

There's an adb Python interface now, and system/core needs to be in
the PYTHONPATH for `import adb` to find it.

Change-Id: I712767a2ba96cb017ce5857dc367e4cacf2ec51f
diff --git a/envsetup.sh b/envsetup.sh
index 62802df..3c29e88 100644
--- a/envsetup.sh
+++ b/envsetup.sh
@@ -198,6 +198,7 @@
     fi
 
     export PATH=$ANDROID_BUILD_PATHS$PATH
+    export PYTHONPATH=$T/system/core:$PYTHONPATH
 
     unset ANDROID_JAVA_TOOLCHAIN
     unset ANDROID_PRE_BUILD_PATHS