Fix build when product.version is mangled (#679)

Strip line breaks when reading product.version, as Git can mangle the line breaks if autocrlf is configured, resulting in `SM_BUILD_TAG` getting defined with a linebreak.

tools/buildbot/generate_headers.py

@@ -50,7 +50,7 @@ def output_version_headers():
     count, shorthash, longhash = get_git_version()
 
   with open(os.path.join(SourceFolder, 'product.version')) as fp:
-    contents = fp.read()
+    contents = fp.read().strip()
   m = re.match('(\d+)\.(\d+)\.(\d+)-?(.*)', contents)
   if m == None:
     raise Exception('Could not detremine product version')