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
@@ -32,7 +32,8 @@
 
 # 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
+# Copy without source permissions because the source could be read-only,
+# but we need to write into the copied folder.
 file(COPY .
   DESTINATION ${clang_cmake_builddir}
   NO_SOURCE_PERMISSIONS
diff --git a/llvm/cmake/modules/CMakeLists.txt b/llvm/cmake/modules/CMakeLists.txt
--- a/llvm/cmake/modules/CMakeLists.txt
+++ b/llvm/cmake/modules/CMakeLists.txt
@@ -99,9 +99,12 @@
 
 # For compatibility with projects that include(LLVMConfig)
 # via CMAKE_MODULE_PATH, place API modules next to it.
+# Copy without source permissions because the source could be read-only,
+# but we need to write into the copied folder.
 # This should be removed in the future.
 file(COPY .
   DESTINATION ${llvm_cmake_builddir}
+  NO_SOURCE_PERMISSIONS
   FILES_MATCHING PATTERN *.cmake
   PATTERN CMakeFiles EXCLUDE
   )
diff --git a/mlir/cmake/modules/CMakeLists.txt b/mlir/cmake/modules/CMakeLists.txt
--- a/mlir/cmake/modules/CMakeLists.txt
+++ b/mlir/cmake/modules/CMakeLists.txt
@@ -42,9 +42,12 @@
 
 # For compatibility with projects that include(MLIRConfig)
 # via CMAKE_MODULE_PATH, place API modules next to it.
+# Copy without source permissions because the source could be read-only,
+# but we need to write into the copied folder.
 # This should be removed in the future.
 file(COPY .
   DESTINATION ${mlir_cmake_builddir}
+  NO_SOURCE_PERMISSIONS
   FILES_MATCHING PATTERN *.cmake
   PATTERN CMakeFiles EXCLUDE
   )