internal/rosa/llvm: set exclusive bit

This was missed when improving bootstrap.

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

internal/rosa/llvm.go

@@ -274,7 +274,9 @@ func (t Toolchain) newLLVM() (pkg.Artifact, string) {
 	}
 
 	version := t.Version(llvmSource)
-	return t.NewPackage("llvm", version, t.Load(llvmSource), nil, &CMakeHelper{
+	return t.NewPackage("llvm", version, t.Load(llvmSource), &PackageAttr{
+		Flag: TExclusive,
+	}, &CMakeHelper{
 		Append: []string{"llvm"},
 
 		Cache: cache,