re: Unidata#2521

Charlie Zender has discovered that the netcdf created file VERSION
conflicts with the C++ version file on OSX case-insensitive file systems,
and maybe other case-insensitvie file systems.

Note:
1. Cmake does not create the VERSION file
2. The VERSION file is not installed
3. It turns out that the VERSION file is not required by the autoconf build.

It is possible that clients or package build system (e.g apt or brew)
might use the VERSION file, so we cannot delete it altogether.

So as a fix, we move the creation of the VERSION file to after the
build is complete by inserting a all-local hook into netcdf-c/Makefile.am.

# Misc. other changes
1. Suppressed warning by making use of the systeminfo command contingent on the platform being Windows.