nocc: stage-0 bootstrap path (binaries gitignored)

Sets up the cc-free fresh-checkout flow without yet committing the
stage-0 binaries. The pieces are in place; flipping the switch is
one `git add -f` away when the compiler is judged stable.

  bootstrap/<arch>/{ww,6c,6a,6l}   stage-0 binaries (gitignored)
  bootstrap/README.md              layout + workflow

Two new targets:

  make bootstrap-snapshot   populates bootstrap/$(ARCH)/ from the
                            currently-built wwstage
  make nocc                 starts from bootstrap/$(ARCH)/, rebuilds
                            the wwstage from source, gates on
                            stage-0 == rebuilt byte-for-byte. Lands
                            in $(OUT)/nocc/ so $(OUT)/ stays
                            untouched. cc is never invoked.

The fixed-point gate has the same shape as `make bootstrap`, just
the entry point flipped: that target trusts cstage; nocc trusts
the checked-in (or local-snapshot) stage-0 binaries.

Implementation notes:

- libwwrt.a is assembled with stage-0 6a, members ordered to match
  $(RT_OBJ) so the embedded symbol table reproduces the cstage
  build byte-for-byte.
- The driver's default lib path is $self_dir/../../lib, which under
  $(NOCC_BIN) resolves to $(NOCC_OUT)/lib (libwwrt only). Each
  ww-build invocation passes -I $(CURDIR)/lib so `use os` etc.
  resolve to source.
- Stage-0 binaries are duplicated under both natural names (ww/6c/
  6a/6l) and _ww-suffixed names so the wwstage driver's
  hard-coded join_path_lit(self_dir, "6c_ww") still finds them.
  When cmd/wwc/ gets deleted at v1.0, that duplication and the
  _ww suffix in the driver both go away.

Makefile

@@ -307,4 +307,78 @@ bootstrap: all
 	@echo "  - cmd/6l/  : ww-6l    (linker w/ archive support) — byte-identical to C 6l (test 992)"
 	@echo "  - cmd/ww/  : ww-driver (build/run/version) — byte-identical to C ww (test 993)"
 
-.PHONY: all cstage wwstage test install clean bootstrap
+# ---- nocc: bootstrap from a checked-in stage-0 binary, no cc -----------
+# A fresh-checkout flow that never invokes cc. Mirrors `make bootstrap`'s
+# fixed-point check but uses `bootstrap/$(ARCH)/{ww,6c,6a,6l}` as the
+# starting point and lands in $(OUT)/nocc/ so the cstage build under
+# $(OUT)/ stays untouched. See bootstrap/README.md and BOOTSTRAP.md.
+#
+# `make bootstrap-snapshot` populates bootstrap/$(ARCH)/ from the
+# currently-built wwstage so you can verify locally before deciding
+# to commit the binaries.
+ARCH		?= amd64
+STAGE0		= bootstrap/$(ARCH)
+NOCC_OUT	= $(OUT)/nocc
+NOCC_BIN	= $(NOCC_OUT)/bin
+NOCC_LIB	= $(NOCC_OUT)/lib
+NOCC_OBJ	= $(NOCC_OUT)/obj
+
+bootstrap-snapshot: wwstage
+	@mkdir -p $(STAGE0)
+	@cp $(BIN)/ww_ww $(STAGE0)/ww
+	@cp $(BIN)/6c_ww $(STAGE0)/6c
+	@cp $(BIN)/6a_ww $(STAGE0)/6a
+	@cp $(BIN)/6l_ww $(STAGE0)/6l
+	@echo "snapshot: $(STAGE0)/{ww,6c,6a,6l} populated from $(BIN)/*_ww"
+	@echo "         (gitignored — 'git add -f bootstrap/$(ARCH)/*' to ship)"
+
+nocc:
+	@for f in ww 6c 6a 6l; do \
+		test -x $(STAGE0)/$$f || { \
+			echo "$@: missing $(STAGE0)/$$f"; \
+			echo "$@: run 'make bootstrap-snapshot' first, or read bootstrap/README.md"; \
+			exit 1; \
+		}; \
+	done
+	@echo "=== nocc: starting from $(STAGE0) (no cc invoked) ==="
+	@rm -rf $(NOCC_OUT)
+	@mkdir -p $(NOCC_BIN) $(NOCC_LIB) $(NOCC_OBJ)
+	@# Stage 0: drop bootstrap binaries under both natural names and
+	@# the _ww-suffixed names the driver expects when shelling out.
+	@for f in ww 6c 6a 6l; do \
+		cp $(STAGE0)/$$f $(NOCC_BIN)/$$f; \
+		cp $(STAGE0)/$$f $(NOCC_BIN)/$${f}_ww; \
+	done
+	@# Assemble libwwrt.a using stage-0 6a — the linker needs it for
+	@# every wwstage-built binary in the next stage. Member order
+	@# follows $(RT_S) so the embedded symbol table matches the
+	@# cstage-built libwwrt.a (cstage uses ar rcs $(RT_OBJ), same
+	@# order).
+	@objs=""; for s in $(RT_S); do \
+		b=`basename $$s .s`; \
+		$(NOCC_BIN)/6a -o $(NOCC_OBJ)/$$b.o $$s; \
+		objs="$$objs $(NOCC_OBJ)/$$b.o"; \
+	done; $(AR) rcs $(NOCC_LIB)/libwwrt.a $$objs
+	@echo "=== stage 1: stage-0 rebuilds the wwstage tools from source ==="
+	@# The driver's default lib path is $self_dir/../../lib — under
+	@# $(NOCC_BIN) that resolves to $(NOCC_OUT)/lib (libwwrt only).
+	@# Pass -I $(CURDIR)/lib so `use os` etc. resolve to source.
+	@cd $(NOCC_BIN) && ./ww build -I $(CURDIR)/selfhost/cmd/wwc \
+		-I $(CURDIR)/lib $(CURDIR)/selfhost/cmd/6c/main.ww && mv main 6c_ww1
+	@cd $(NOCC_BIN) && ./ww build -I $(CURDIR)/selfhost/cmd/6a \
+		-I $(CURDIR)/selfhost/cmd/wwc -I $(CURDIR)/lib \
+		$(CURDIR)/selfhost/cmd/6a/main.ww && mv main 6a_ww1
+	@cd $(NOCC_BIN) && ./ww build -I $(CURDIR)/selfhost/cmd/6l \
+		-I $(CURDIR)/selfhost/cmd/wwc -I $(CURDIR)/lib \
+		$(CURDIR)/selfhost/cmd/6l/main.ww && mv main 6l_ww1
+	@cd $(NOCC_BIN) && ./ww build -I $(CURDIR)/selfhost/cmd/wwc \
+		-I $(CURDIR)/lib $(CURDIR)/selfhost/cmd/ww/main.ww && mv main ww_ww1
+	@echo "=== fixed-point gates: rebuilt tools == stage-0 binaries? ==="
+	@cmp $(NOCC_BIN)/6c_ww1 $(STAGE0)/6c && echo "  6c ✓"
+	@cmp $(NOCC_BIN)/6a_ww1 $(STAGE0)/6a && echo "  6a ✓"
+	@cmp $(NOCC_BIN)/6l_ww1 $(STAGE0)/6l && echo "  6l ✓"
+	@cmp $(NOCC_BIN)/ww_ww1 $(STAGE0)/ww && echo "  ww ✓"
+	@echo
+	@echo "NOCC OK: $(STAGE0)/* reproduces itself from source. cc not invoked."
+
+.PHONY: all cstage wwstage test install clean bootstrap nocc bootstrap-snapshot