Add groups="pdk-cw-fs" for [external/squashfs-tools]

This ensures the squashfs includes are available to
[system/extras/squashfs_utils]
Change-Id: Ia35bfb165b052da44daecf0908d94124b2157bcb

default.xml

@@ -252,7 +252,7 @@
   <project path="external/sonivox" name="platform/external/sonivox" groups="pdk" />
   <project path="external/speex" name="platform/external/speex" groups="pdk" />
   <project path="external/sqlite" name="platform/external/sqlite" groups="pdk" />
-  <project path="external/squashfs-tools" name="platform/external/squashfs-tools" />
+  <project path="external/squashfs-tools" name="platform/external/squashfs-tools" groups="pdk-cw-fs" />
   <project path="external/srtp" name="platform/external/srtp" groups="pdk-cw-fs" />
   <project path="external/stlport" name="platform/external/stlport" groups="pdk" />
   <project path="external/strace" name="platform/external/strace" groups="pdk-cw-fs" />