[Diffusion] rL246607: [MC] Generate a timestamp for COFF object files

[NAKAMURA Takumi via llvm-commits]

chapuni added inline comments.

/llvm/trunk/lib/MC/WinCOFFObjectWriter.cpp:1018 FYI, before r196341,

  Header.TimeDateStamp = sys::TimeValue::now().toEpochTime();

TimeValue::toEpochTime() returns uint64_t. Seems 2038-compliant.
/llvm/trunk/lib/MC/WinCOFFObjectWriter.cpp:1021 GNU Bintutils AS doesn't set TimeDataStamp.
It makes difficult to check identity in bootstrap builder.
See compare_23 in http://bb.pgr.jp/builders/clang-3stage-i686-cygwin/builds/1184

I hope it optional.

  - Configurable with ENABLE_TIMESTAMPS. (Tweaked in r246905)
  - Suppress the feature for targeting cygming.
  - Introduce an option for it. GNU LD has --[no-]insert-timestamp.
  - Introduce an comparator in llvm-obj* that ignores timestamp and checksum.

Users:
  majnemer (Author)
  grosbach (Auditor)

http://reviews.llvm.org/rL246607