Support for cross compiled C to native CMS and a C library.
Except for the added makefile an unmodified version of zlib-1.2.8
is cross compiled to zlib.txtlib.
[gas2asm] (https://github.com/jphartmann/gas2asm) converts the -S
output from gcc to HLASM input. Required.
[txtlib] (https://github.com/jphartmann/CMS-TXTLIB) generates the
target libraries when object decks can be created at the workstation.
OPtional.