[lldb] Fix deps loading for lldb-python on Windows and Python3.8+ (llvm#9370)

Author: weliveindetail

lldb/bindings/python/CMakeLists.txt

@@ -198,6 +198,24 @@ function(finish_swig_python swig_target lldb_python_bindings_dir lldb_python_tar
       COMMENT "Copying Python DLL to LLDB binaries directory.")
   endif()
 
+  # Since Python3.8 the Windows runtime loads dependent DLLs only from the directory of the binary
+  # itself (and not Path). Windows has no RPATHs, so we must copy all DLLs that we depend on into
+  # the Python package.
+  if (WIN32)
+    # TARGET_RUNTIME_DLLS is supported in CMake 3.21+
+    if ("${CMAKE_VERSION}" VERSION_LESS "3.21.0")
+      if (LLDB_INCLUDE_TESTS)
+        message(SEND_ERROR
+          "Your CMake version is ${CMAKE_VERSION}. In order to run LLDB tests "
+          "on Windows please upgrade to 3.21.0 at least (or disable tests with "
+          "LLDB_INCLUDE_TESTS=Off)")
+      endif()
+    else()
+      add_custom_command(TARGET ${swig_target} POST_BUILD
+        COMMAND ${CMAKE_COMMAND} -E copy -t ${lldb_python_target_dir} $<TARGET_RUNTIME_DLLS:liblldb>
+        COMMAND_EXPAND_LISTS)
+    endif()
+  endif()
 
 endfunction()