Build for musl linux

[mattip]

In order to build musl linux artifacts, we need to add it to the github action which uses multibuild. But the Pr to add musl to multibuild seems stalled multi-build/multibuild#430

[mattip]

multibuild has been updated. This now needs a build with MB_ML_LIBC="musllinux" and MB_ML_VER="_1_1"