[COFF] don't replace import library if contents are unchanged
Summary:
This detects when an import library is about to be overwritten with a
newly built one with the same contents, and keeps the old library
instead. The use case for this is to avoid needlessly rebuilding
targets that depend on the import library in build systems that rely
on timestamps to determine whether a target requires rebuilding.
This feature was requested in PR35917.
Reviewers: rnk, ruiu, zturner, pcc
Reviewed By: ruiu
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D42326
llvm-svn: 323164
2 files changed