HDF5: ExtProj needs to use GLOBAL to use from parent projects #877

Job	Run time
CMake Serial Minimal Build on Linux	48s
CMake build on MacOS	6m 46s
CMake Serial With Clawpack Build on Linux	6m 55s
CMake Serial With Clawpack and HDF Build on Linux	8m 31s
CMake Serial With GeoClaw Build on Linux	1m 14s
CMake Serial With CudaClaw (CUDA 10.1) Build on Linux	3m 10s
CMake Serial With CudaClaw (CUDA 11.3) Build on Linux	3m 57s
CMake MPI Minimal Build on Linux	1m 22s
CMake MPI With Clawpack Build on Linux	7m 33s
CMake MPI With Clawpack and HDF Build on Linux	8m 51s
CMake MPI With GeoClaw Build on Linux	2m 14s
CMake MPI With CudaClaw (CUDA 10.1) Build on Linux	5m 5s
CMake MPI With CudaClaw (CUDA 11.3) Build on Linux	5m 11s
CMake MPI With ThunderEgg Build on Linux	3m 52s
	1h 5m 29s

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