Check if mirror VFD and subfiling VFD are enabled before adding their (#5055)

respective utils subdirectories.

Fixes #4984.

Author: lrknox

utils/CMakeLists.txt

@@ -7,8 +7,12 @@ endif ()
 
 option (HDF5_BUILD_UTILS  "Build HDF5 Utils" ON)
 if (HDF5_BUILD_UTILS)
-  add_subdirectory (mirror_vfd)
-  add_subdirectory (subfiling_vfd)
+  if (HDF5_ENABLE_MIRROR_VFD)  
+    add_subdirectory (mirror_vfd)
+  endif ()
+  if (HDF5_ENABLE_SUBFILING_VFD)  
+    add_subdirectory (subfiling_vfd)
+  endif ()
 endif ()
 
 #-- Add the h5dwalk and test executables