Add -mfma for AVX512DQ tests.

CMakeLists.txt

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 5dfea22..23ea1ec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -248,7 +248,7 @@
 
   option(EIGEN_TEST_AVX512DQ "Enable/Disable AVX512DQ in tests/examples" OFF)
   if(EIGEN_TEST_AVX512DQ)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mavx512dq")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -mavx512dq -mfma")
     message(STATUS "Enabling AVX512DQ in tests/examples")
   endif()