Adds a new option -alt_module_dir which specifies an alternate directory in which to look for libraries in a modules.log offline drcachesim file. Hooks the option up to the opcode_mix and view tools and to raw2trace (both its standalone launcher and drcachesim frontend integration).
This will be useful in general, but is needed for adding tests with checked-in raw files and binaries, where the checked-in modules.log has a hardcoded path that will never match all test environments.
Adds a test that runs both raw2trace and opcode_mix on a new checked-in aarch64 raw trace (this test will evolve for future cross-arch testing, which is the reason for using aarch64). The binaries are stripped, with the two libraries "fake" binaries: libmemtrace.so is not executed, and libdynamorio.so is only used for dynamorio_sigreturn, so these are synthetic binaries (created from asm files) to keep them smaller. The tests deliberately fail on x86 and match an error message that will improve when architecture tags are added.
Issue: #4318