Add globally defined __TARGET and __CPU to phoenix-rtos-build

[gerard5]

Description

Adds globally visible defines (through C/XXFLAGS) pointing to TARGET architecture and CPU. The definitions are derived from TARGET_FAMILY and TARGET_SUBFAMILY.

Motivation and Context

Need of include target specific headers in phoenix-rtos-devices, libphoenix, etc.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

How Has This Been Tested?

• Already covered by automatic testing.
• New test added: (add PR link here).
• Tested by hand on: imxrt1176-nil, ia32-generic.

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (list the PRs, preferably in merge-order).
• I will merge this PR by myself when appropriate.

[nalajcie]

one small thing worth consideration (not sure which is better, use whatever version you would like).

I'm assuming the currently-existing defines like KERNEL_TARGET_DEFINE=-DCPU_IMXRT106X -DNOMMU would be removed in separate PR after necessary changes in submodules.

[gerard5]

one small thing worth consideration (not sure which is better, use whatever version you would like).

I'm assuming the currently-existing defines like KERNEL_TARGET_DEFINE=-DCPU_IMXRT106X -DNOMMU would be removed in separate PR after necessary changes in submodules.

#146 Done