remove ubuntu platform from HWPACKS

This allows the script to work for another release like "precise"
without having to update it
diff --git a/build-images.py b/build-images.py
index c5adac9..32c87ce 100755
--- a/build-images.py
+++ b/build-images.py
@@ -30,8 +30,8 @@
 
 # a mapping of hwpack name to l-m-c name
 HWPACKS = {
-    'lt-panda-oneiric': 'panda',
-    'overo-oneiric': 'overo',
+    'lt-panda': 'panda',
+    'overo': 'overo',
 }
 # a mapping of binary image to its image_file size
 BINARIES = {
@@ -92,8 +92,8 @@
     args = ('bzip2', imgfile)
     cmd_runner.run(args).wait()
 
-def build_image(outdir, hwpack, hwpack_file, binary, binary_file):
-    imgfile = "%s/%s_%s.img" %(outdir,hwpack,binary)
+def build_image(outdir, platform, hwpack, hwpack_file, binary, binary_file):
+    imgfile = "%s/%s-%s_%s.img" %(outdir,hwpack,platform,binary)
     print "building image: %s" % imgfile
     dev = HWPACKS[hwpack]
     size = BINARIES[binary]
@@ -145,13 +145,14 @@
     today_hwpacks = db.get_todays_hwpacks()
 
     for hwpack in hwpacks:
-        url = hwpack_available(today_hwpacks, hwpack)
+        hwpackname = "%s-%s" % (hwpack, args.platform)
+        url = hwpack_available(today_hwpacks, hwpackname)
         if url is not None and url is not False:
             hwpf = dm.download(url, None)
             for binary in binaries:
                 (date,url) = db.get_latest_binary(binary)
                 binaryf = dm.download(url, None)
-                build_image(args.out_dir, hwpack, hwpf, binary, binaryf)
+                build_image(args.out_dir, args.platform, hwpack, hwpf, binary, binaryf)
         else:
             print 'No hwpack for %s' % hwpack