Accept Git trailer Build-Id

… in place of Piper tag BUILD_NUMBER, to avoid corrupting Git trailers.

(cherry picked from commit 0e24f1d)

Issue: 296119824
Reviewed-on: youtube/cobalt#2013
Reviewed-on: youtube/cobalt#2018

cobalt/build/gyp_cobalt

@@ -47,7 +47,7 @@ COMMIT_COUNT_BUILD_NUMBER_OFFSET = 1000000
 # Matches numbers > 1000000. The pattern is basic so git log --grep is able to
 # interpret it.
 GIT_BUILD_NUMBER_PATTERN = r'[1-9]' + r'[0-9]' * 6 + r'[0-9]*'
-BUILD_NUMBER_TAG_PATTERN = r'^BUILD_NUMBER={}$'
+BUILD_NUMBER_TAG_PATTERN = r'^(Build-Id: |BUILD_NUMBER=){}$'
 
 # git log --grep can't handle capture groups.
 BUILD_NUBER_PATTERN_WITH_CAPTURE = '({})'.format(GIT_BUILD_NUMBER_PATTERN)
@@ -160,7 +160,7 @@ def GetBuildNumberFromCommits():
       BUILD_NUMBER_TAG_PATTERN.format(BUILD_NUBER_PATTERN_WITH_CAPTURE),
       flags=re.MULTILINE)
   match = full_pattern_with_capture.search(output)
-  return match.group(1) if match else None
+  return match.group(2) if match else None
 
 
 def GetBuildNumberFromServer():