[InlineCost] Add flag to allow changing the default inline cost
It can be useful to tune the default inline threshold without overriding other inlining thresholds (e.g. in code compiled for size).
The existing -inline-threshold flag overrides other thresholds, so it is insufficient in codebases where there is a mix of code compiled for size and speed.
Patch by Michael Holman <firstname.lastname@example.org>
Reviewers: eraman, tejohnson
Reviewed By: tejohnson
Subscribers: tejohnson, mtrofin, davidxl, hiraditya, haicheng, llvm-commits
Differential Revision: https://reviews.llvm.org/D73217