internal/rosa/go: alternative bootstrap path

For targets where the bootstrap toolchain is not available.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/rosa/go.go

@@ -63,18 +63,54 @@ ln -s \
 }
 
 func (t Toolchain) newGoLatest() pkg.Artifact {
+	var (
+		bootstrapEnv   []string
+		bootstrapExtra []pkg.Artifact
+
+		finalEnv []string
+	)
+	switch runtime.GOARCH {
+	case "amd64":
+		bootstrapExtra = append(bootstrapExtra, t.newGoBootstrap())
+
+	case "arm64":
+		bootstrapEnv = append(bootstrapEnv,
+			"GOROOT_BOOTSTRAP=/system",
+		)
+		bootstrapExtra = append(bootstrapExtra,
+			t.Load(Binutils),
+
+			t.Load(GMP),
+			t.Load(MPFR),
+			t.Load(MPC),
+
+			t.Load(Zlib),
+			t.Load(Libucontext),
+
+			t.Load(gcc),
+		)
+
+		finalEnv = append(finalEnv, "CGO_ENABLED=0")
+
+	default:
+		panic("unsupported target " + runtime.GOARCH)
+	}
+
 	go119 := t.newGo(
 		"1.19",
 		"9_e0aFHsIkVxWVGsp9T2RvvjOc3p4n9o9S8tkNe9Cvgzk_zI2FhRQB7ioQkeAAro",
-		[]string{"CGO_ENABLED=0"}, `
+		append(bootstrapEnv, "CGO_ENABLED=0"), `
 rm \
 	crypto/tls/handshake_client_test.go \
+	cmd/pprof/pprof_test.go \
 	os/os_unix_test.go
+sed -i \
+	's/os\.Getenv("GCCGO")$/"nonexistent"/' \
+	go/internal/gccgoimporter/importer_test.go
 echo \
 	'type syscallDescriptor = int' >> \
 	os/rawconn_test.go
-`, t.newGoBootstrap(),
-	)
+`, bootstrapExtra...)
 
 	go121 := t.newGo(
 		"1.21.13",
@@ -97,7 +133,7 @@ echo \
 	go123 := t.newGo(
 		"1.23.12",
 		"wcI32bl1tkqbgcelGtGWPI4RtlEddd-PTd76Eb-k7nXA5LbE9yTNdIL9QSOOxMOs",
-		nil, `
+		[]string{"CGO_ENABLED=0"}, `
 sed -i \
 	's,/lib/ld-musl-`+linuxArch()+`.so.1,/system/bin/linker,' \
 	cmd/link/internal/`+runtime.GOARCH+`/obj.go
@@ -107,7 +143,7 @@ sed -i \
 	go125 := t.newGo(
 		"1.25.6",
 		"x0z430qoDvQbbw_fftjW0rh_GSoh0VJhPzttWk_0hj9yz9AKOjuwRMupF_Q0dbt7",
-		nil, `
+		finalEnv, `
 sed -i \
 	's,/lib/ld-musl-`+linuxArch()+`.so.1,/system/bin/linker,' \
 	cmd/link/internal/`+runtime.GOARCH+`/obj.go