Makefile: drop non-Linux cross-compile targets

The updated libcontainer (part of runc) doesn't compile as cleanly on
non-Linux platforms.  We could work around some of the types not being
defined on those platforms, as we do in later branches, but for now, and
unless we need to for downstream consumers, this gets us to passing CI
faster.

Signed-off-by: Nalin Dahyabhai <[email protected]>

Author: nalind

Makefile

@@ -71,7 +71,7 @@ bin/buildah: $(SOURCES) cmd/buildah/*.go
 buildah: bin/buildah
 
 .PHONY: cross
-cross: bin/buildah.darwin.amd64 bin/buildah.linux.386 bin/buildah.linux.amd64 bin/buildah.linux.arm64 bin/buildah.linux.arm bin/buildah.linux.mips64 bin/buildah.linux.mips64le bin/buildah.linux.mips bin/buildah.linux.mipsle bin/buildah.linux.ppc64 bin/buildah.linux.ppc64le bin/buildah.linux.riscv64 bin/buildah.linux.s390x bin/buildah.windows.amd64.exe
+cross: bin/buildah.linux.386 bin/buildah.linux.amd64 bin/buildah.linux.arm64 bin/buildah.linux.arm bin/buildah.linux.mips64 bin/buildah.linux.mips64le bin/buildah.linux.mips bin/buildah.linux.mipsle bin/buildah.linux.ppc64 bin/buildah.linux.ppc64le bin/buildah.linux.riscv64 bin/buildah.linux.s390x
 
 bin/buildah.%:
 	mkdir -p ./bin