This patch is adding support for dynamic shadow allocation.
This is a merge and re-commit of the following patches.
[compiler-rt] Fix Asan build on Android https://reviews.llvm.org/D24768 [compiler-rt] Add support for the dynamic shadow allocation https://reviews.llvm.org/D23363
This patch needed to re-land at the same time:
[asan] Support dynamic shadow address instrumentation https://reviews.llvm.org/D23354