diff --git a/gnu/packages/llvm.scm b/gnu/packages/llvm.scm
index 33d863ae11..896b7afb47 100644
--- a/gnu/packages/llvm.scm
+++ b/gnu/packages/llvm.scm
@@ -382,6 +382,52 @@ output), and Binutils.")
 (define-public clang-toolchain-10
   (make-clang-toolchain clang-10))
 
+(define (make-clang-tools-extra clang)
+  ;; XXX: An attempt to build clang-tools-extra outside the Clang tree.
+  (package
+    (inherit clang)
+    (name "clang-tools-extra")
+    (source (origin
+              (method url-fetch)
+              (uri (llvm-download-uri "clang-tools-extra"
+                                      (package-version llvm-10)))
+              (sha256
+               (base32
+                "074ija5s2jsdn0k035r2dzmryjmqxdnyg4xwvaqych2bazv8rpxc"))
+              (patches (search-patches "clang-tools-extra-cmake.patch"))))
+    (arguments
+     '(#:build-type "Release"
+       #:phases (modify-phases %standard-phases
+                  (add-before 'configure 'copy-clang-cmake-module
+                    (lambda* (#:key inputs #:allow-other-keys)
+                      (let ((clang-source (assoc-ref inputs "clang-source")))
+                        (mkdir "../clang-source")
+                        (with-directory-excursion "../clang-source"
+                          (invoke "tar" "xf" clang-source))
+
+                        ;; 'cmake/modules' is in the search path of the
+                        ;; top-level 'CMakeLists.txt', so copy it there.
+                        (install-file (car (find-files "../clang-source"
+                                                       "^AddClang\\.cmake$"))
+                                      "cmake/modules")
+                        #t)))
+                  (add-before 'build 'augment-header-path
+                    (lambda _
+                      (let ((context-h (car (find-files "../clang-source"
+                                                        "^Context\\.h$"))))
+                        (setenv "CPATH"
+                                (string-append (dirname
+                                                (canonicalize-path context-h))
+                                               ":" (getenv "CPATH")))
+                        #t))))))
+    (inputs
+     `(("clang" ,clang)
+       ("clang-source", (package-source clang))
+       ,@(package-inputs clang)))))
+
+(define-public clang-tools-extra-10
+  (make-clang-tools-extra clang-10))
+
 (define-public llvm-9
   (package
     (inherit llvm-10)
diff --git a/gnu/packages/patches/clang-tools-extra-cmake.patch b/gnu/packages/patches/clang-tools-extra-cmake.patch
new file mode 100644
index 0000000000..96672bb2dd
--- /dev/null
+++ b/gnu/packages/patches/clang-tools-extra-cmake.patch
@@ -0,0 +1,38 @@
+diff --git a/CMakeLists.txt b/CMakeLists.txt
+index 57bb970..6e5de7c 100644
+--- a/CMakeLists.txt
++++ b/CMakeLists.txt
+@@ -1,3 +1,33 @@
++cmake_minimum_required(VERSION 3.4.3)
++
++project(Clang-Tools-Extra)
++
++find_package(LLVM REQUIRED HINTS "${LLVM_CMAKE_PATH}")
++list(APPEND CMAKE_MODULE_PATH ${LLVM_DIR})
++
++# This is the place where we put Clang's 'AddClang.cmake'.
++list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules")
++
++set(LLVM_TOOLS_BINARY_DIR ${TOOLS_BINARY_DIR} CACHE PATH "Path to llvm/bin")
++set(LLVM_LIBRARY_DIR ${LIBRARY_DIR} CACHE PATH "Path to llvm/lib")
++set(LLVM_MAIN_INCLUDE_DIR ${INCLUDE_DIR} CACHE PATH "Path to llvm/include")
++set(LLVM_BINARY_DIR ${LLVM_OBJ_ROOT} CACHE PATH "Path to LLVM build tree")
++set(LLVM_MAIN_SRC_DIR ${MAIN_SRC_DIR} CACHE PATH "Path to LLVM source tree")
++
++set(PACKAGE_VERSION "${LLVM_PACKAGE_VERSION}")
++
++include(AddClang)
++include(AddLLVM)
++include(TableGen)
++include(HandleLLVMOptions)
++include(VersionFromVCS)
++include(LLVMDistributionSupport)
++
++# Dummy targets to appease CMake.  These are normally found in the
++# Clang tree.
++add_custom_target(clang-resource-headers)
++add_custom_target(ClangSACheckers)
++
+ include(CMakeDependentOption)
+ 
+ add_subdirectory(clang-apply-replacements)