internal/rosa/llvm: use llvm build system

This removes the multistep bootstrap hack. Stage0 exceptions are also eliminated for a later change to bring the stage0 distribution down to just a bare toolchain, toybox and shell. This change also enables dynamic linking and ThinLTO.

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

cmd/mbf/main.go

@@ -318,7 +318,7 @@ func main() {
 
 				if err = cm.Do(func(cache *pkg.Cache) (err error) {
 					pathname, _, err = cache.Cure(
-						(t - 2).Load(rosa.Clang),
+						(t - 2).Load(rosa.LLVM),
 					)
 					return
 				}); err != nil {
@@ -328,7 +328,7 @@ func main() {
 
 				if err = cm.Do(func(cache *pkg.Cache) (err error) {
 					pathname, checksum[0], err = cache.Cure(
-						(t - 1).Load(rosa.Clang),
+						(t - 1).Load(rosa.LLVM),
 					)
 					return
 				}); err != nil {
@@ -337,7 +337,7 @@ func main() {
 				log.Println("stage2:", pathname)
 				if err = cm.Do(func(cache *pkg.Cache) (err error) {
 					pathname, checksum[1], err = cache.Cure(
-						t.Load(rosa.Clang),
+						t.Load(rosa.LLVM),
 					)
 					return
 				}); err != nil {
@@ -542,7 +542,7 @@ func main() {
 					presets[i] = p
 				}
 
-				base := rosa.Clang
+				base := rosa.LLVM
 				if !flagWithToolchain {
 					base = rosa.Musl
 				}