ncopts global variable is not used properly with shared libraries on MacOSX

[vfonov]

The error happens when mincresample is used with minc1 file on MacOSX, with libminc compiled as shared library.
While resampling a standard 3D volume with X,Y,Z dimension, mincresample tries to iterate over all possible dimensions and exclude their information from copying headers ( see https://github.com/BIC-MNI/minc-tools/blob/develop/progs/mincresample/mincresample.c#L1365 ).
By setting ncopts=0, it is supposed to prevent libminc from bailing, however on MacOSX the global variable ncopts inside mincresample points to a different location then from within libminc, which leads to failure when vector dimension is queried ( https://github.com/BIC-MNI/minc-tools/blob/develop/progs/mincresample/mincresample.c#L1393 ) and netcdf fails, causing mincresample to exit.

Looking with a debugger:
in the context of mincresample:
(lldb) p &ncopts
(int *) $2 = 0x00000001000cdf44

and in the context of libminc:
(lldb) p &ncopts
(int *) $4 = 0x00000001008c7be4

[vfonov]

So, this happens when libminc is build as shared library, and netcdf is build as static library.