openblas: choose generic target for x86 and x86_64.

[gt7-void]

The current template uses DYNAMIC_ARCH=1 to get multiple versions of some
functions to support different cpus. However, it will pick up the cpu it was
compiled in as a minimum requirement for the common code.

Adding TARGET=GENERIC fixes this, now the common code is compiled for a generic cpu.

See #29604 and OpenMathLib/OpenBLAS#3139.

Have the results of the proposed changes been tested?

• I use the packages affected by the proposed changes on a regular basis and confirm this PR works for me

[ericonr]

Can you confirm this fixed the issue you were experiencing? Should probably verify by building on a machine with AVX available and transferring to the other.

I'd consider using GENERIC for all DYNAMIC_ARCH builds, if applicable.

[gt7-void]

Can you confirm this fixed the issue you were experiencing? Should probably verify by building on a machine with AVX available and transferring to the other.

Yes, I built the package on a skylake, installed it on nehalem, and it works.

I'd consider using GENERIC for all DYNAMIC_ARCH builds, if applicable.

I didn't want to touch the other archs because I don't have hardware to test. But since the other arches all set TARGET to some value, at least the output will not depend on the machine it's compiled on. Also, TARGET=ARMV8 looks generic enough.

[ericonr]

Thanks!