[build][Linux] Create preset to run LLVM's TSan libdispatch tests
Build a separate compiler-rt instance for running the tests. It is built
and tested against an installed toolchain instead of the llvm-build-dir.
Install everything we need to run tests (CMake modules, FileCheck, etc.)
into the toolchain directory.
Add synthetic target 'all' for llvm-install-components. Also we must set
LLVM_INSTALL_UTILS=ON, so the utilities required by tests (e.g.,
FileCheck) are included in the install target.
rdar://49396529
