[CMake] Contribute Find-module to CMake vs Config-file to upstream

[Brad King]

On 05/22/2018 10:06 PM, Paul Fultz II wrote:
> Or pkg-config could be extended to fix the issues.

The `.pc` file format is too flat to lend itself well to representing
all the information we need.  A goal of `.cps` files is to teach
pkg-config to parse them and respond to its standard queries with the
same output format as now.

> In the Boost Cmake Modules, we support generating both pkg-config and
> cmake config files automatically from the cmake targets:

That's fantastic but until there is no such thing as a Boost installation
that doesn't support both tools the problems will persist.  They mangle
their library names in such a way that it's impossible to use boost without
a build system that memorizes dozens of mangling conventions that vary
with the version of boost, version of the compiler, architecture, etc.

-Brad