uavo hash: ensure that uavo hash is stable across OSes

In python, os.walk() is not sorted.  This can result in the
hash being computed over the files in different orders on
different OSes, or even after touching a directory.

This ensures that the files are considered in lexical order
so that the hash is stable.

make/scripts/version-info.py

@@ -258,6 +258,11 @@ def GetHashofDirs(directory, verbose=0):
     
   try:
     for root, dirs, files in os.walk(directory):
+      # os.walk() is unsorted.  Must make sure we process files in sorted order so
+      # that the hash is stable across invocations and across OSes.
+      if files:
+          files.sort()
+
       for names in files:
         if verbose == 1:
           print 'Hashing', names
@@ -269,18 +274,30 @@ def GetHashofDirs(directory, verbose=0):
           f1.close()
           continue
 
-	while 1:
-	  # Read file in as little chunks
-  	  buf = f1.read(4096)
-	  if not buf : break
-	  SHAhash.update(hashlib.sha1(buf).hexdigest())
+        # Compute file hash.  Same as running "sha1sum <file>".
+        f1hash = hashlib.sha1()
+        while 1:
+          # Read file in as little chunks
+          buf = f1.read(4096)
+          if not buf : break
+          f1hash.update(buf)
         f1.close()
 
+        if verbose == 1:
+          print 'Hash is', f1hash.hexdigest()
+
+        # Append the hex representation of the current file's hash into the cumulative hash
+        SHAhash.update(f1hash.hexdigest())
+
   except:
     import traceback
     # Print the stack traceback
     traceback.print_exc()
     return -2
+
+  if verbose == 1:
+      print 'Final hash is', SHAhash.hexdigest()
+
   hex_stream = lambda s:",".join(['0x'+hex(ord(c))[2:].zfill(2) for c in s])
   return hex_stream(SHAhash.digest())