Add compiler flag in 3rdparty cmake file to suppress warning on newer clang compilers

Fit/3rdparty/RootMinimizers/CMakeLists.txt

@@ -19,6 +19,13 @@ add_definitions(-DWARNINGMSG)
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DMATH_NO_PLUGIN_MANAGER -DHAS_MINUIT2 -DR__HAS_MATHMORE")
 if(NOT WIN32)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-deprecated-declarations")
+    # The following code suppresses a warning in
+    # Fit/3rdparty/RootMinimizers/mathcore/Math/GSLRngROOTWrapper.h
+    # which is issued in newer versions of clang.
+    if(CMAKE_CXX_COMPILER_ID STREQUAL "Clang"
+        AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL 10)
+      set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-dangling-gsl")
+    endif()
 else()
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /wd4244 /wd4267")
 endif()