--- a/cmake/modules/AddQuadMathFlags.cmake	2020-03-24 07:54:22.548925006 +0100
+++ b/cmake/modules/AddQuadMathFlags.cmake.patched	2020-03-24 22:53:43.127262894 +0100
@@ -0,0 +1,28 @@
+# Defines the functions to use QuadMath
+#
+# .. cmake_function:: add_dune_quadmath_flags
+#
+#    .. cmake_param:: targets
+#       :positional:
+#       :single:
+#       :required:
+#
+#       A list of targets to use QuadMath with.
+#
+
+
+function(add_dune_quadmath_flags _targets)
+  if(QUADMATH_FOUND)
+    foreach(_target ${_targets})
+      target_link_libraries(${_target} "quadmath")
+      set_property(TARGET ${_target}
+        APPEND_STRING
+        PROPERTY COMPILE_FLAGS "-DENABLE_QUADMATH=1 -D_GLIBCXX_USE_FLOAT128=1 ")
+      if(${CMAKE_CXX_COMPILER_ID} STREQUAL GNU)
+        set_property(TARGET ${_target}
+          APPEND_STRING
+          PROPERTY COMPILE_FLAGS "-fext-numeric-literals ")
+      endif()
+    endforeach(_target ${_targets})
+  endif(QUADMATH_FOUND)
+endfunction(add_dune_quadmath_flags)