[AutoUpgrade] Fix a compatibility issue with module flag

[AutoUpgrade] Fix a compatibility issue with module flag

Summary:
After r304661, module flag to record objective-c image info section is
encoded without whitespaces after comma. The new name is equivalent to
the old one, except that when LTO a module built by old compiler and a
module built by a new compiler, it will fail with conflicting values.

Fix the issue by removing whitespaces in bitcode upgrade path.

rdar://problem/34416934

Reviewers: compnerd

Reviewed By: compnerd

Subscribers: mehdi_amini, hans, llvm-commits

Differential Revision: https://reviews.llvm.org/D37909

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@313398 91177308-0d34-0410-b5e6-96231b3b80d8