Minor cleanups to run_code_generation.

Prints more info when a particular file is not found.

Bug: angleproject:3333
Change-Id: I11ceb0d319023cd1fd23fd25297e5367030342a0
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1550899
Reviewed-by: Yuly Novikov <ynovikov@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>

scripts/run_code_generation.py

@@ -13,7 +13,7 @@ import os
 import subprocess
 import sys
 
-script_dir = os.path.abspath(os.path.dirname(os.path.abspath(__file__)))
+script_dir = sys.path[0]
 root_dir = os.path.abspath(os.path.join(script_dir, '..'))
 
 # auto_script is a standard way for scripts to return their inputs and outputs.
@@ -106,6 +106,7 @@ def any_hash_dirty(name, filenames, new_hashes, old_hashes):
     for filename in filenames:
         key = name + ":" + filename
         if not os.path.isfile(filename):
+            print('Could not find %s for %s' % (filename, name))
             found_dirty_hash = True
         else:
             new_hashes[key] = md5(filename)
@@ -115,12 +116,13 @@ def any_hash_dirty(name, filenames, new_hashes, old_hashes):
 
 
 def any_old_hash_missing(new_hashes, old_hashes):
+    result = False
     for name, _ in old_hashes.iteritems():
         if name not in new_hashes:
             script, file = name.split(':')
-            print('%s missing from generated hashes.' % file)
-            return True
-    return False
+            print('%s missing from generated hashes for %s.' % (file, script))
+            result = True
+    return result
 
 
 def update_output_hashes(script, outputs, new_hashes):
@@ -134,6 +136,7 @@ def update_output_hashes(script, outputs, new_hashes):
 
 def main():
     os.chdir(script_dir)
+
     old_hashes = json.load(open(hash_fname))
     new_hashes = {}
     any_dirty = False