[scudo] Allow for compile-time choice of the SizeClassMap
Summary:
With this change, we allow someone to chose the `SizeClassMap` they want to use
at compile time via a define.
I feel somewhat unimaginative with the name of the defines, so if someone has a
better idea, let me know. I have been alternating between those and
`SCUDO_USE_xxx_SIZECLASSMAP` which is clearer but also longer. The issue with
those is that it wouldn't be consistent with `SCUDO_TSD_EXCLUSIVE` that should
probably become `SCUDO_USE_EXCLUSIVE_TSD` maybe?
Anyway, naming is hard, and I am not sure what makes more sense!
Reviewers: alekseyshl, flowerhack
Reviewed By: alekseyshl
Subscribers: llvm-commits, srhines
Differential Revision: https://reviews.llvm.org/D40521
llvm-svn: 319350