Fix syntax error
Fix syntax error

The include_files argument was malformed due to a missing `${` at the beginning.  Was expanding to (e.g.) the literal `Zstd_INCLUDE_DIRS}` instead of to the contents of the `Zstd_INCLUDE_DIRS` variable.
Unidata/netcdf-c,Unidata/netcdf-c,Unidata/netcdf-c,Unidata/netcdf-c