auto-generate .md table of CPU supported platforms from Cmake CI

[ahbarnett]

using Marco's .py matrix generator for cmake CI combos.

Eg:

Table of supported platforms: Let’s try to automate, at least CPU for 2.3:  generate .md snippet, to be literalincluded into install.rst  and README.md (or link to):

Platform/compiler  | CPU Release  |  CPU debug |

—-----------------------------------------------------

linux/gcc                |    check | check | ……

linux/clang            |   check  | check