Spec M36 — multi-target builds (owner, 2026-09-03; last in the queue)

Goal: one mc build produces every configured output — macOS, Linux, Windows, wasm32, wasm64 — from one source tree and one mc.toml. Depends on the target registry (M17), the foreign targets (M16, M17, M19, M20, M33) and sysroot resolution (M25).

mc.toml #

[project]
name = "app"
entry = "main.mc"

[[targets]]              # each entry is a complete target; keys not given fall back to the
name = "mac"             # single-target sections ([target], [linker], [sysroot], [libs], [externs])
os = "macos"  arch = "aarch64"  kind = "exe"  out = "build/app-macos-arm64"

[[targets]]
name = "linux"
os = "linux"  arch = "aarch64"  out = "build/app-linux-arm64"
linker.cmd = "ld.lld"    # dotted keys override the shared [linker] for this target only

[[targets]]
name = "web"
os = "browser"  arch = "wasm32"  out = "build/app.wasm"

• mc build with [[targets]] present builds all of them, in file order, stopping at the first failure (exit 1) unless --keep-going; mc build --target=NAME builds one; mc build --list-targets prints the table (name, os, arch, kind, out, resolved sysroot).
• Outputs never collide: out is required per target (or defaults to build/<name>-<os>-<arch>[.ext]), and the driver refuses two targets with the same out.
• The taught compiler ([compiler]) is built once and reused for every target; per-target [limits] and [run] are allowed.
• mc limits and mc build --limits report per target; [run] entries let mc build --run execute each output through its runner (native, Docker, node, wine) when configured.
• Determinism: building the same target alone or as part of --all yields byte-identical outputs (tested by cmp).

Acceptance #

examples/minimal and examples/wasm gain [[targets]] covering every available target on the machine; mc build produces all outputs; --list-targets is deterministic; CI runs the macOS and wasm entries and the Linux entry through the two-stage job; docs/guide/50-cross-compile.md documents the section.

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