nco fails to build when compiling with "--no-undefined -Wl" as ld flags about nco HOT 1 OPEN

NCO defines some one-liner functions that access global variables, like nco_prg_nm_get(), in a part of the nco.h header only visible to source files that include main(), e.g., ncks.c. Thus the library contains only the function prototype, not the function definition. We would need a PR to refactor the nco.h header, and probably all the source files that contain main(), in order for --no-undefined -Wl to succeed. I was never sure of the best way to handle access to global variables by the library. Hopefully a volunteer will figure out a solution that is still moderately elegant and avoids redundant code.

from nco.