Merge change 2717 into donut

* changes:
  build images with minigzip instead of system gzip
diff --git a/tools/releasetools/common.py b/tools/releasetools/common.py
index 51a6d8f..686c6ef 100644
--- a/tools/releasetools/common.py
+++ b/tools/releasetools/common.py
@@ -81,12 +81,13 @@
 
   p1 = Run(["mkbootfs", os.path.join(sourcedir, "RAMDISK")],
            stdout=subprocess.PIPE)
-  p2 = Run(["gzip", "-n"], stdin=p1.stdout, stdout=ramdisk_img.file.fileno())
+  p2 = Run(["minigzip"],
+           stdin=p1.stdout, stdout=ramdisk_img.file.fileno())
 
   p2.wait()
   p1.wait()
   assert p1.returncode == 0, "mkbootfs of %s ramdisk failed" % (targetname,)
-  assert p2.returncode == 0, "gzip of %s ramdisk failed" % (targetname,)
+  assert p2.returncode == 0, "minigzip of %s ramdisk failed" % (targetname,)
 
   cmdline = open(os.path.join(sourcedir, "cmdline")).read().rstrip("\n")
   p = Run(["mkbootimg",