internal/rosa/llvm: early-runtimes for gentoo stage only

This bootstrap step is not required for a native Rosa OS stage0 distribution.

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

internal/rosa/llvm.go

@@ -64,7 +64,7 @@ func init() {
 		meta.Version = _meta.Version
 
 		early := _muslHeaders
-		if t.stage.isStage0() {
+		if t.stage.isStage0() && !t.stage.isRosa() {
 			// The LLVM build system uses the system installation when building with
 			// LLVM_LINK_LLVM_DYLIB, since it builds runtimes after the fact, using
 			// the just-built toolchain. This is unacceptable in stage0 due to the