llgo/ssa.SetRuntime: prevent multiple loading of runtime

cl/compile.go

@@ -465,6 +465,9 @@ func NewPackage(prog llssa.Program, pkg *ssa.Package, files []*ast.File) (ret ll
 	pkgProg := pkg.Prog
 	pkgTypes := pkg.Pkg
 	pkgName, pkgPath := pkgTypes.Name(), llssa.PathOf(pkgTypes)
+	if pkgPath == llssa.PkgRuntime {
+		prog.SetRuntime(pkgTypes)
+	}
 	ret = prog.NewPackage(pkgName, pkgPath)
 
 	ctx := &context{

cl/compile_test.go

@@ -20,6 +20,7 @@ import (
 	"testing"
 
 	"github.com/goplus/llgo/cl/cltest"
+	"github.com/goplus/llgo/ssa"
 )
 
 func testCompile(t *testing.T, src, expected string) {
@@ -36,7 +37,7 @@ func TestFromTestdata(t *testing.T) {
 }
 
 func TestRuntime(t *testing.T) {
-	cltest.Pkg(t, "github.com/goplus/llgo/internal/runtime", "../internal/runtime/llgo_autogen.ll")
+	cltest.Pkg(t, ssa.PkgRuntime, "../internal/runtime/llgo_autogen.ll")
 }
 
 func TestVar(t *testing.T) {