[llvm] [Runtimes] Merge 'compile_commands.json' files from runtimes build (PR #116303)

[Joseph Huber via llvm-commits]

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@@ -313,3 +313,18 @@ if(SUB_COMPONENTS)
       ${LLVM_BINARY_DIR}/runtimes/Components.cmake)
   endif()
 endif()
+
+# If the user requested 'compile_commands.json' we merge the generated JSON from
+# the created directories.
+if(CMAKE_EXPORT_COMPILE_COMMANDS)
+  file(TO_NATIVE_PATH "${LLVM_MAIN_SRC_DIR}/utils/merge-json.py" MERGE_JSON_PATH)
+  add_custom_command(OUTPUT ${LLVM_BINARY_DIR}/compile_commands.json
+                     COMMAND ${CMAKE_COMMAND} -E touch ${LLVM_BINARY_DIR}/compile_commands.json
+                     COMMAND ${CMAKE_COMMAND} -E touch ${CMAKE_BINARY_DIR}/compile_commands.json
+                     COMMAND ${Python3_EXECUTABLE} ${MERGE_JSON_PATH}
+                             ${LLVM_BINARY_DIR}/compile_commands.json   
+                             ${CMAKE_BINARY_DIR}/compile_commands.json
+                             -o ${LLVM_BINARY_DIR}/compile_commands.json   
+                     DEPENDS ${CMAKE_BINARY_DIR}/compile_commands.json)
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jhuber6 wrote:

Yeah I'm not 100% positive on how this will work out. When I test it under normal circumstances (fresh build and modification of files) it works fine. however if I manually delete the compile_commands.json it will get into a dumb state where it keeps thinking it's not  there.

https://github.com/llvm/llvm-project/pull/116303