Add macOS support for the Mimer SQL QtSql plugin

Make sure the Mimer SQL include files and libraries are found
to enable the Mimer SQL QtSql plugin.

Fixes: QTBUG-111219
Pick-to: 6.6
Change-Id: Ieee0e26f3689dd373fda81c98180066927d25b40
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

cmake/FindMimer.cmake

@@ -43,6 +43,9 @@ else()
             else()
                 set(MimerSQL_library_hints "")
             endif()
+        elseif(APPLE AND ${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
+            set(MimerSQL_library_hints "/usr/local/lib")
+            set(MimerSQL_include_dir_hints "/usr/local/include")
         else()
             set(MimerSQL_include_dir_hints "")
             set(MimerSQL_library_hints "")