Add rpath for libc++ libraries in order to not specify rpath by user
each time. Disable -frthlib-add-ppath by default for VE similar to other
architectures. Update regression tests to check modifications.
Change C++ header files placement to support multiple LLVM_RUNTIME_TARGETS
build. Also modifies regression test for it.
Reviewed By: simoll
Differential Revision: https://reviews.llvm.org/D114527
Optimize toolchain regression test for VE by removing not a useful test
(-fuse-init-array test) and merge several tests to one test which checks
default behavior of driver. Also add sysroot to reduce conflicts.
These are suggested in https://reviews.llvm.org/D92996.
Thank you so much.
Reviewed By: MaskRay
Differential Revision: https://reviews.llvm.org/D93084
