Clang package.py: Don't run 'git diff' before building

If there is a diff, build.py will nuke the repository anyway. And in
pathological circumstances (see bug), printing the diff can take a very
long time.

Bug: 1014241
Change-Id: Ic045dfef66c7695b07ba9099352744d5becdcdfd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1862916Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#705937}

tools/clang/scripts/package.py

@@ -178,15 +178,6 @@ def main():
     platform = 'Linux_x64'
 
   with open('buildlog.txt', 'w') as log:
-    if os.path.exists(LLVM_DIR):
-      Tee('Diff in llvm:\n', log)
-      cwd = os.getcwd()
-      os.chdir(LLVM_DIR)
-      TeeCmd(['git', 'status'], log, fail_hard=False)
-      TeeCmd(['git', 'diff'], log, fail_hard=False)
-      os.chdir(cwd)
-    else:
-      Tee('No previous llvm checkout.\n', log)
     Tee('Starting build\n', log)
 
     # Do a clobber build.