newt: Fix autogenerated linker script usage

PreNewtError instead of NewNewtError was causing crashes. Also
"autogenerated" key should be handled when there is only one
value ("autogenerated") inside the vals slice.

newt/pkg/bsp_package.go

@@ -113,15 +113,7 @@ func (bsp *BspPackage) resolveLinkerScriptSetting(
 			return nil, err
 		}
 
-		if path == "autogenerated" {
-			path, err = bsp.getAutogeneratedLinkerScriptPath()
-			if err != nil {
-				return nil, util.PreNewtError(err,
-					"Could not resolve autogenerated linker script path for target \"%s\"",
-					bsp.yov.Pkg.Name())
-			}
-			paths = append(paths, path)
-		} else if path != "" {
+		if path != "" {
 			paths = append(paths, path)
 		}
 	} else {
@@ -130,9 +122,19 @@ func (bsp *BspPackage) resolveLinkerScriptSetting(
 		// Read each linker script from the list.
 		for _, val := range vals {
 			if val == "autogenerated" {
-				return nil, util.PreNewtError(err,
-					"Both autogenerated and custom linker scripts cannot be used."+
+				if len(vals) > 1 {
+					return nil, util.NewNewtError("Both autogenerated and custom linker scripts cannot be used. " +
 						"Newt handles either autogenerated linker script or a list of custom linker scripts.")
+				} else {
+					path, err := bsp.getAutogeneratedLinkerScriptPath()
+					if err != nil {
+						return nil, util.PreNewtError(err,
+							"Could not resolve autogenerated linker script path for target \"%s\"",
+							bsp.yov.Pkg.Name())
+					}
+					paths = append(paths, path)
+					continue
+				}
 			}
 
 			path, err := proj.ResolvePath(ypkg.Repo().Path(), val)