build: support multiple link files in a package

cl/compile.go

@@ -123,7 +123,8 @@ const (
 	PkgLLGo
 	PkgNoInit   // noinit: a package that don't need to be initialized
 	PkgDeclOnly // decl: a package that only have declarations
-	PkgLinkOnly // link: a package that don't need to be compiled but need to be linked
+	PkgLinkIR   // link llvm ir (.ll)
+	// PkgLinkBitCode // link bitcode (.bc)
 )
 
 type pkgInfo struct {

cl/import.go

@@ -91,7 +91,9 @@ func PkgKindOf(pkg *types.Package) int {
 func pkgKind(v string) int {
 	switch v {
 	case "link":
-		return PkgLinkOnly
+		return PkgLinkIR
+	// case "link:bc":
+	//	return PkgLinkBitCode
 	case "decl":
 		return PkgDeclOnly
 	case "noinit":