diff --git a/clang/cmake/modules/CMakeLists.txt b/clang/cmake/modules/CMakeLists.txt
--- a/clang/cmake/modules/CMakeLists.txt
+++ b/clang/cmake/modules/CMakeLists.txt
@@ -32,8 +32,10 @@
 
 # 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
   )