[lldb][cmake] Fix lldb_python_target_dir in unusual build configurations (#202492)
The lldb binary, when running regression tests, will search for Python
bindings relative to itself. Normally,
`${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}` is consistent with that path,
but both Arm and Qualcomm build toolchains using a configuration where
that doesn't work.
Fix the configuration to use LLVM_RUNTIME_OUTPUT_INTDIR as the source of
truth for where lldb will be installed. This is the variable used to
determine where the lldb binary is located in the build directory, so it
will always be consistent.