diff --git a/CMakeLists.txt b/CMakeLists.txt
index feef2e1a678..582d76e79c3 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -222,6 +222,20 @@ if (COMPILER_CLANG)
 
     # Display absolute paths in error messages. Otherwise KDevelop fails to navigate to correct file and opens a new file instead.
     set(COMPILER_FLAGS "${COMPILER_FLAGS} -fdiagnostics-absolute-paths")
+
+    # We cannot afford to use LTO when compiling unitests, and it's not enough
+    # to only supply -fno-lto at the final linking stage. So we disable it
+    # completely.
+    if (NOT ENABLE_TESTS)
+        # Link time optimization
+        set (CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS_RELWITHDEBINFO} -flto=thin")
+        set (CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS_RELWITHDEBINFO} -flto=thin")
+        set (CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO "${CMAKE_EXE_LINKER_FLAGS_RELWITHDEBINFO} -flto=thin")
+    endif ()
+
+    # Always prefer llvm tools when using clang. For instance, we cannot use GNU ar when llvm LTO is enabled
+    set (CMAKE_AR "llvm-ar")
+    set (CMAKE_RANLIB "llvm-ranlib")
 endif ()
 
 option (ENABLE_LIBRARIES "Enable all libraries (Global default switch)" ON)