[CMake][Clang] Copy folder without permissions

[sebastian-ne]

Summary

Copying the folder keeps the original permissions by default. This
creates problems when the source folder is read-only, e.g. in a
packaging environment.
Then, the copied folder in the build directory is read-only as well.
Later on, with configure_file, ClangConfig.cmake is copied into that
directory (in the build tree), failing when the directory is read-only.

Fix that problem by copying the folder without keeping the original
permissions.

[tstellar]

LGTM.

Those pre-commit failure seem to be unrelated.

[Ericson2314]

LGMT. Also thanks I saw the same failures and was worried they were not spurious on my own patch. Glad to know they are!

[awarzynski]

What about similar code in LLVM?

clang/cmake/modules/CMakeLists.txt

35

[nit] This comment tells me "what" is happening here, but that can be deduced from the code (i.e. NO_SOURCE_PERMISSIONS --> copy without source permissions). Explaining "why" this being read-only is a problem would be more helpful, IMHO.

clang/cmake/modules/CMakeLists.txt

configure_file(
   ${CMAKE_CURRENT_SOURCE_DIR}/ClangConfig.cmake.in
   ${clang_cmake_builddir}/ClangConfig.cmake
   @ONLY)
 set(CLANG_CONFIG_CMAKE_DIR)
 set(CLANG_CONFIG_LLVM_CMAKE_DIR)
 
 # For compatibility with projects that include(ClangConfig)
 # via CMAKE_MODULE_PATH, place API modules next to it.
+# Copy without source permissions because the source could be read-only
 file(COPY .
   DESTINATION ${clang_cmake_builddir}
+  NO_SOURCE_PERMISSIONS
   FILES_MATCHING PATTERN *.cmake
   PATTERN CMakeFiles EXCLUDE
   )
 
 # Generate ClangConfig.cmake for the install tree.
 find_prefix_from_config(CLANG_CONFIG_CODE CLANG_INSTALL_PREFIX "${CLANG_INSTALL_PACKAGE_DIR}")
 set(CLANG_CONFIG_CMAKE_DIR "\${CLANG_INSTALL_PREFIX}/${CLANG_INSTALL_PACKAGE_DIR}")
 set(CLANG_CONFIG_LLVM_CMAKE_DIR "\${CLANG_INSTALL_PREFIX}/${LLVM_INSTALL_PACKAGE_DIR}")