port: rewrite bootstrap tool in Go

Replace the Python bootstrap script with a Go implementation that
cross-compiles to native binaries for Linux and macOS on x86_64 and
aarch64. The Go port preserves all sections of the original (system
packages, optional Flatpak GUI apps, custom downloads, and the macOS
firecracker VM bridge) and adds first-class pacman support so the tool
works on Arch-family distros alongside Debian, RHEL, and macOS.

A Makefile produces a host binary via `make build` and the full
four-target matrix under dist/ via `make build-all`.

Makefile

@@ -0,0 +1,44 @@
+BINARY := bootstrap_environment
+DIST   := dist
+PKG    := .
+
+# Statically-linked, stripped binaries for distribution.
+GOFLAGS := -trimpath -ldflags="-s -w"
+
+TARGETS := \
+	linux/amd64 \
+	linux/arm64 \
+	darwin/amd64 \
+	darwin/arm64
+
+.PHONY: all build build-all test vet fmt clean
+
+all: build
+
+build:
+	go build $(GOFLAGS) -o $(BINARY) $(PKG)
+
+# Cross-compile native binaries for each supported (OS, arch) pair into dist/.
+build-all: $(DIST)
+	@for t in $(TARGETS); do \
+		os=$${t%/*}; arch=$${t#*/}; \
+		out=$(DIST)/$(BINARY)-$$os-$$arch; \
+		echo "==> $$os/$$arch -> $$out"; \
+		CGO_ENABLED=0 GOOS=$$os GOARCH=$$arch \
+			go build $(GOFLAGS) -o $$out $(PKG) || exit 1; \
+	done
+
+$(DIST):
+	mkdir -p $(DIST)
+
+test:
+	go test ./...
+
+vet:
+	go vet ./...
+
+fmt:
+	gofmt -w .
+
+clean:
+	rm -rf $(DIST) $(BINARY)