Properly exclude hosttests/tools/tests directories

There was a typo that resulted in the ignored directory names being
concatenated rather than included individually in the list. This caused
us to unintentionally publish the "wrong" sources for all releases
since Mar 23, 2012.

Bug: 30798902
Change-Id: I51e3ad48c4487374fe5614d074c1c0f091d430e0
(cherry picked from commit 31dde68d9c361dbdbe9092918f8224da2471b576)
diff --git a/build/tools/mk_sources_zip.py b/build/tools/mk_sources_zip.py
index 76b5b9e..3220e3a 100755
--- a/build/tools/mk_sources_zip.py
+++ b/build/tools/mk_sources_zip.py
@@ -39,7 +39,7 @@
         self.CNT_NOPKG = 0
         # DIR is the list of directories to scan in TOPDIR.
         self.DIR = "frameworks libcore"
-        self.IGNORE_DIR = [ "hosttests" "tools" "tests" ]
+        self.IGNORE_DIR = [ "hosttests", "tools", "tests" ]
         # IGNORE is a list of namespaces to ignore. Must be java
         # package definitions (e.g. "com.blah.foo.")
         self.IGNORE = [ "sun.", "libcore.", "dalvik.",