[Hexagon] Fix compiler-rt install dir type, scope sanitizers (#209375)
COMPILER_RT_INSTALL_LIBRARY_DIR must be CACHE STRING, not CACHE PATH: a
relative PATH-typed cache entry resolves against the runtimes sub-build
directory instead of CMAKE_INSTALL_PREFIX, misplacing sanitizer libs.
Replace the explicit COMPILER_RT_BUILD_* ON list with
COMPILER_RT_SANITIZERS_TO_BUILD=all, since those options already default
ON upstream and infeasible sanitizers self-exclude via their own
ALL_<X>_SUPPORTED_ARCH lists.
Add FORCE to the dylib overrides so they take effect after
hexagon-unknown-linux-musl-clang-dist.cmake has already cached them OFF.