internal/rosa: make toolchain optional

The final Rosa OS image does not need the toolchain.

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

internal/rosa/rosa.go

@@ -225,6 +225,8 @@ const (
 	TExclusive = 1 << iota
 	// TEarly hints for an early variant of [Toybox] to be used when available.
 	TEarly
+	// TNoToolchain excludes the LLVM toolchain.
+	TNoToolchain
 )
 
 var (
@@ -309,15 +311,18 @@ mkdir -vp /work/system/bin
 		if flag&TEarly != 0 {
 			toybox = toyboxEarly
 		}
-		support = slices.Concat(extra, []pkg.Artifact{
+		std := []pkg.Artifact{cureEtc{newIANAEtc()}, musl}
-			cureEtc{newIANAEtc()},
+		toolchain := []pkg.Artifact{compilerRT, runtimes, clang}
-			musl,
+		utils := []pkg.Artifact{
-			compilerRT,
-			runtimes,
-			clang,
 			boot.Load(Mksh),
 			boot.Load(toybox),
-		})
+		}
+
+		if flag&TNoToolchain != 0 {
+			toolchain = nil
+		}
+
+		support = slices.Concat(extra, std, toolchain, utils)
 		env = fixupEnviron(env, []string{
 			EnvTriplet + "=" + triplet(),
 			lcMessages,