Build joltc as a self-contained binary (make joltc-release / joltc-debug)

host/chez/build-joltc.ss builds joltc into target/<profile>/joltc: it emits a
flat source of the full runtime + compiler image + inlined build.ss + every
jolt-core/stdlib file as a baked string literal + a cli.ss-style launcher, then
(in a fresh Chez, so the inlined runtime's redefinition of error doesn't strand
early references and runtime eval still sees the runtime's top-level procedures)
compiles it and cc-links it with the Chez petite/scheme boots and the launcher
stub embedded as C arrays. The launcher reads those arrays via FFI on
(jolt-materialize-bundles!) and registers them so build-self-contained can spill
them. joltc itself is cc-linked (clean signature for Homebrew); only the apps it
later builds use the appended-stub path.

build.ss: skip the csv toolchain check on the self-contained path and create the
build dir with a subprocess-free bld-mkdir-p, so a  from the
distributed binary shells out to nothing.

release = optimize-level 3 + no inspector info + compressed; debug =
optimize-level 0 + inspector + procedure source + debug-on-exception.

joltc-selfbuild-smoke.sh (make joltcsmoke) builds joltc and, with an empty
environment (no chez/cc/PATH), drives it through the build-app fixture, asserting
the produced binary's output. .gitignore ignores target/.

.gitignore

@@ -2,6 +2,7 @@ AGENTS.md
 .DS_Store
 CLAUDE.md
 build/
+target/
 .clj-kondo/
 .dirge/
 .claude/