jolt build: compile an app to a standalone binary (Phase 4 stages 1-2)

Restores the standalone-binary capability the Janet host had. `bin/joltc build
-m NS -o OUT` AOT-compiles an app into a single self-contained executable — the
whole runtime, clojure.core, stdlib and compiler embedded, no Chez install or
jolt source needed at runtime.

Pipeline (host/chez/build.ss, host primitive jolt.host/build-binary driven by
jolt.main's build command): resolve deps, load the entry namespace recording the
app namespaces in dependency order, re-emit each to Scheme, textually inline the
cli.ss runtime load sequence into one flat source + the app + a launcher, then
compile-file -> make-boot-file -> embed the boot as C bytes -> cc-link against
libkernel.a.

Two non-obvious bits: the compile pass runs in a fresh Chez, not the loaded
runtime (regex.ss shadows top-level `error`, which otherwise bakes a broken
reference into the boot); and the launcher installs scheme-start rather than
running -main at top level, since boot top-level forms execute during heap build
before argv is set, so args only reach -main through scheme-start.

Loader: a require of an in-memory namespace with no source file now no-ops, so
AOT'd app namespaces satisfy require in a built binary.

Mode flags (--opt/--dev, default release) are plumbed; the optimization passes
they gate come in a later stage. RFC 0007 has the design. Gated by `make
buildsmoke`.

host/chez/build-smoke.sh

@@ -0,0 +1,32 @@
+#!/bin/sh
+# build smoke: `jolt build` compiles a multi-namespace app (macro + cross-ns +
+# clojure.string) into a standalone binary, which then runs with no jolt source
+# or Chez install on the path — args reach -main, output matches.
+root="$(CDPATH= cd -- "$(dirname -- "$0")/../.." && pwd)"
+cd "$root"
+
+app="$root/test/chez/build-app"
+out="$(mktemp -d)/app-bin"
+trap 'rm -rf "$(dirname "$out")"' EXIT
+
+echo "build smoke: compiling app.core -> $out"
+if ! JOLT_PWD="$app" bin/joltc build -m app.core -o "$out" >/dev/null 2>&1; then
+  echo "  FAIL: jolt build exited non-zero"
+  exit 1
+fi
+[ -x "$out" ] || { echo "  FAIL: no executable produced"; exit 1; }
+
+# Run from a neutral cwd with args; check the three output lines.
+got="$(cd / && "$out" alpha bb ccc 2>&1)"
+want='HELLO FROM A BUILT BINARY!
+HELLO FROM A BUILT BINARY!
+args: [alpha bb ccc]
+sum: 10'
+if [ "$got" = "$want" ]; then
+  echo "build smoke: passed"
+else
+  echo "  FAIL: binary output mismatch"
+  echo "--- want ---"; echo "$want"
+  echo "--- got ----"; echo "$got"
+  exit 1
+fi