Using tools when building for a platform

[oliverlee]

I would like to be able to specify that a binary should be built for a specific platform and run it under gdb

toolchains_arm_gnu/examples/bzlmod on  HEAD (2f22aa8) [!] via  6GiB/8GiB | 6GiB/7GiB
❯  bazel run --platforms=//custom/platform:cortex_m3 --run_under=@arm_none_eabi//:gdb //custom:binary

However, this fails as gdb is constrained

toolchains_arm_gnu/toolchain/templates/top.BUILD

Lines 23 to 36 in 2f22aa8

	native_binary(
	name = tool,
	src = select({
	host: "@%toolchain_name%_{}//:{}".format(host, tool)
	for host in hosts["%toolchain_prefix%"].keys()
	}),
	out = tool,
	target_compatible_with = select({
	host: constraint_values
	for host, constraint_values in hosts["%toolchain_prefix%"].items()
	} | {
	"//conditions:default": ["@platforms//:incompatible"],
	}),
	)

Is there a specific reason to constrain the binaries in this way?

If not, would it make sense to remove target_compatible_with and set

src = "@%toolchain_name%_{}//:{}".format(_normalize(HOST_CONSTRAINTS), tool),

similar to how the toolchain alias is created for custom toolchains?

toolchains_arm_gnu/toolchain/templates/toolchain.bazel

Lines 125 to 130 in 2f22aa8

	if _normalize(os) == host.os and _normalize(cpu) == host.cpu:
	native.alias(
	name = name,
	actual = ":{}_{}".format(name, host_repo),
	visibility = visibility,
	)

[oliverlee]

I've created a pull request but feel free to close it if you think this is the wrong direction.