debug consistency: fix unused-but-set-variable warning #655

Job	Run time
Automake Serial Minimal Build on Linux	2m 23s
Automake Serial With Clawpack Build on Linux	7m 43s
Automake Serial With Clawpack and HDF Build on Linux	7m 29s
Automake Serial With GeoClaw Build on Linux	5m 10s
Automake Serial With CudaClaw (CUDA 10.1) Build on Linux	4m 39s
Automake Serial With CudaClaw (CUDA 11.3) Build on Linux	4m 18s
Automake MPI Minimal Build on Linux	4m 29s
Automake MPI Debug With CXX Build on Linux	7m 8s
Automake MPI With Clawpack Build on Linux	8m 28s
Automake MPI With Clawpack and HDF Build on Linux	8m 48s
Automake MPI With GeoClaw Build on Linux	5m 17s
Automake MPI With CudaClaw (CUDA 10.1) Build on Linux	4m 1s
Automake MPI With CudaClaw (CUDA 11.3) Build on Linux	4m 9s
Automake MPI With ThunderEgg Build on Linux	7m 34s
	1h 21m 36s

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