conditionals for platform-specific MAKE_ENV options

[Brook Milligan <brook%nmsu.edu@localhost>]

I am trying to make a package that has the following notes about compiling:

- If you see compilation errors, try make sse2only=1 to disable SSE4 code.

- It also works with ARM CPUs supporting the NEON instruction sets. To compile for 32 bit ARM architectures (such as ARMv7), use make arm_neon=1. To compile for for 64 bit ARM architectures (such as ARMv8), use make arm_neon=1 aarch64=1.

I am assuming that I should include a conditional based upon MACHINE_PLATFORM to set MAKE_ENV so that (at least some of) these cases are handled.  However, I am not sure what the conditional should be.  Thus, I have several questions.

- I know that SSE4 was introduced a long time ago, but are there any relevant platforms that should still use the sse2only=1 option?

- What is the best way to handle conditionals for the two ARM architectures mentioned above?

Thanks for your help.

Cheers,
Brook