FEAT: save static results in NetCDF format

[Dengda98]

Before this PR, the static results are written into stdout, and ASCII format is inconvenient for code maintainance.
NetCDF format perfectly matched the static results, since I use -X and -Y to define the 2D grid instead the 1D distance array in dynamic case.

ncdump -h looks like,

$ ncdump -h stgrn.nc 
netcdf stgrn {
dimensions:
        north = 21 ;
        east = 21 ;
variables:
        double north(north) ;
        double east(east) ;
        double EXZ(north, east) ;
        double EXR(north, east) ;
        double VFZ(north, east) ;
        double VFR(north, east) ;
        double HFZ(north, east) ;
        double HFR(north, east) ;
        double HFT(north, east) ;
        double DDZ(north, east) ;
        double DDR(north, east) ;
        double DSZ(north, east) ;
        double DSR(north, east) ;
        double DST(north, east) ;
        double SSZ(north, east) ;
        double SSR(north, east) ;
        double SST(north, east) ;

// global attributes:
                :src_va = 4. ;
                :src_vb = 2.7 ;
                :src_rho = 2.5 ;
                :rcv_va = 4. ;
                :rcv_vb = 2.7 ;
                :rcv_rho = 2.5 ;
                :calc_upar = 0 ;
}

However, common pre-built binary NetCDF only have dynamic library, while static library is needed to build PyGRT. After much consideration, I still decide to build the static libnetcdf.a from source in Github Workflow. During the whole process, there are many dependency issues, directly solving with lots of jobs makes the workflow .yaml file looks dirty. Therefore I saved the final built packages and upload them to another repo (my blog....), and the corresponding jobs become a simple downloading job. Same operations applied to FFTW.

Now the static results are classical NetCDF format, and can be easily plot via GMT.