[mlir] Export python-related .cmake files

[nicolasvasilache]

Summary

This allows downstream projects to build python extensions using the same macros as MLIR.

mlir/cmake/modules/CMakeLists.txt

if (NOT LLVM_INSTALL_TOOLCHAIN_ONLY)
   if(mlir_has_exports)
     install(EXPORT MLIRTargets DESTINATION ${MLIR_INSTALL_PACKAGE_DIR}
             COMPONENT mlir-cmake-exports)
   endif()
 
   install(FILES
     ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/MLIRConfig.cmake
     ${CMAKE_CURRENT_SOURCE_DIR}/AddMLIR.cmake
+    ${CMAKE_CURRENT_SOURCE_DIR}/AddMLIRPythonExtension.cmake
+    ${CMAKE_CURRENT_SOURCE_DIR}/MLIRDetectPythonEnv.cmake
     DESTINATION ${MLIR_INSTALL_PACKAGE_DIR}
     COMPONENT mlir-cmake-exports)
 
   if(NOT LLVM_ENABLE_IDE)
     # Add a dummy target so this can be used with LLVM_DISTRIBUTION_COMPONENTS
     add_custom_target(mlir-cmake-exports)
     add_llvm_install_targets(install-mlir-cmake-exports
                              COMPONENT mlir-cmake-exports)
   endif()
 endif()