Fix has-mmap flag for netcdf crate #233

Job	Run time
rustfmt	1m 25s
conda (ubuntu, conda-forge, stable)	1m 0s
static builds (ubuntu-latest, stable)	1m 24s
conda (windows, conda-forge, stable)	3m 55s
Address sanitizer	1m 43s
conda (macos, conda-forge, stable)	2m 28s
static builds (windows-latest, stable-msvc)	6m 21s
static builds (windows-latest, stable-gnu)	5m 40s
test apt (stable)	33s
static builds (macos-11, stable)	3m 57s
test apt (beta)	42s
static builds (macos-latest, stable)	3m 49s
test apt (nightly)	45s
	33m 42s

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