internal/rosa/llvm: migrate runtimes and clang

This eliminates most newLLVM family of functions.

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

internal/rosa/rosa.go

@@ -328,24 +328,23 @@ mkdir -vp /work/system/bin
 			name += "-std"
 		}
 
-		boot := t - 1
-		runtimes, clang := boot.NewLLVM()
 		toybox := Toybox
 		if flag&TEarly != 0 {
 			toybox = toyboxEarly
 		}
-		std := []pkg.Artifact{cureEtc{newIANAEtc()}, boot.Load(Musl)}
-		toolchain := []pkg.Artifact{boot.Load(LLVMCompilerRT), runtimes, clang}
-		utils := []pkg.Artifact{
-			boot.Load(Mksh),
-			boot.Load(toybox),
-		}
 
+		base := LLVMClang
 		if flag&TNoToolchain != 0 {
-			toolchain = nil
+			base = Musl
 		}
 
-		support = slices.Concat(extra, std, toolchain, utils)
+		support = slices.Concat(extra, (t-1).AppendPresets([]pkg.Artifact{
+			cureEtc{newIANAEtc()},
+		},
+			base,
+			Mksh,
+			toybox,
+		))
 		env = fixupEnviron(env, []string{
 			EnvTriplet + "=" + triplet(),
 			lcMessages,