In the great "Unofficial Aztec C Online Museum" of Bill Buckels I have
found probably the last version of the Manx C compiler that can create
CP/M-86 .CMD files. It is a MS-DOS application (version 4.2b) that
uses cross compiling technology.

However I can not find any information of how to cross compile a
source code to the CP/M-86. Does anybody know how to do that (any
compiler and linker switches, libraries to be used, etc) or have
access to the documentation of this product?

I find this compiler very important because it is probably the only
one CP/M-86 C compiler that fulfills (to some extend) the ANSI C
standard which makes potential porting of existing C applications or
just experimenting with CP/M-86 much easier.