Asan-i386-calls-Dynamic-Test and Asan-i386-inline-Dynamic-Test fail to
run on a x86_64 host. This is because asan's unit test lit files are
configured once, rather than per target arch as with the non-unit
tests. LD_LIBRARY_PATH ends up incorrect, and the tests try linking
against the x86_64 runtime which fails.
This changes the unit test CMake machinery to configure the default
and dynamic unit tests once per target arch, similar to the other asan
tests. Then the fix from https://reviews.llvm.org/D108859 is adapted
to the unit test Lit files with some modifications.