[CMake] Give Python module install command a component name

[xiaobai]

Summary

This install command is used to install all the python modules and
python bindings. Currently the only way to install it is this:
cmake -P build/tools/lldb/tools/scripts/cmake_install.cmake
However with my change you should be able to add "lldb-python-bindings" to
LLVM_DISTRIBUTION_COMPONENTS and invoke ninja install-distribution.
Alternatively, you can do something like
`cmake -DCMAKE_INSTALL_COMPONENT="lldb-python-modules" -P
build/cmake_install.cmake` yourself.

[xiaobai]

This isn't quite doing what I want yet. I intend on adding an install target.

[xiaobai]

Gonna take some time to rethink and better understand this.

[compnerd]

The install- target is created by add_llvm_install_targets, not by the component. The component is part of CMake itself, and is controlled by the CMAKE_INSTALL_DEFAULT_COMPONENT_NAME.

scripts/CMakeLists.txt

add_custom_command(
   VERBATIM
   COMMENT "Python script building LLDB Python wrapper")
 add_custom_target(swig_wrapper ALL DEPENDS ${LLDB_WRAP_PYTHON})
 
 set_source_files_properties(${CMAKE_CURRENT_BINARY_DIR}/lldb.py PROPERTIES GENERATED 1)
 
 
 # Install the LLDB python module
-install(DIRECTORY ${SWIG_PYTHON_DIR} DESTINATION ${SWIG_INSTALL_DIR})
+install(DIRECTORY ${SWIG_PYTHON_DIR}
+  COMPONENT "lldb-python-modules"
+  DESTINATION ${SWIG_INSTALL_DIR})
 
 # build Python modules
 add_subdirectory(Python/modules)