Looking for advice/direction for multiple/custom architecture, multiple/custom OS, (with cpp plugin)

I’m trying to setup gradle to handle building on multiple operating systems and multiple architectures using the cpp plugin. Here is a sample of some of the build types I’m trying to accomplish:

Architecture Operating System Toolchain Notes/Questions
x86 VxWorks Custom executables Can I define custom operating system?
x86 custom hardware VxWorks Custom executables Can I define custom operating system and custom hardware?
x86 LynxOS GCC (in path) Can I define custom operating system and custom hardware?
x86 custom hardware LynxOS GCC (in path) Can I define custom operating system?
ppc Linux(variant for ppc) GCC custom executables Working on this but gradle is complaining about the use of targetPlatform.architecture.ppc?
x86 Linux GCC Done
x86_64 Linux GCC Done
x86 Windows MINGW (on linux) Doable, not tested
x86_64 Windows MINGW (on linux) Doable, not tested
x86 Windows MINGW (on windows) Doable, not tested
x86_64 Windows MINGW (on windows) Doable, not tested
x86 Windows Visual studio (command line) Doable, not tested
x86_64 Windows Visual studio (command line) Doable, not tested

I have found examples of some of this but not sure that I can accomplish everything I’m trying to do. Specifcally in regards to custom operating systems. I found information here on custom architecture https://github.com/gradle/gradle/blob/master/design-docs/continuous-delivery-for-c-plus-plus.md but I’m having difficulty getting existing architectures to work successfully (ppc for instance)