Keep extra-include dirs due to "utility" folder in SourceFile object

Also remove the reference to the original Library object because it's no
more needed.

Author: cmaglie

legacy/builder/container_find_includes.go

@@ -340,9 +340,8 @@ func findIncludesUntilDone(ctx *types.Context, cache *includeCache, sourceFileQu
 		// copy the current search path list and add the library' utility directory
 		// if needed.
 		includeFolders := ctx.IncludeFolders
-		if library := sourceFile.Library; library != nil && library.UtilityDir != nil {
-			includeFolders = append(includeFolders, library.UtilityDir)
-		}
+		if extraInclude := sourceFile.ExtraIncludePath(); extraInclude != nil {
+			includeFolders = append(includeFolders, extraInclude)
 		}
 
 		var preprocErr error

legacy/builder/types/types.go

@@ -27,9 +27,11 @@ type SourceFile struct {
 	// Path to the source file within the sketch/library root folder
 	relativePath *paths.Path
 
-	// Set to the Library object of origin if this source file comes
-	// from a library
-	Library *libraries.Library
+	// ExtraIncludePath contains an extra include path that must be
+	// used to compile this source file.
+	// This is mainly used for source files that comes from old-style libraries
+	// (Arduino IDE <1.5) requiring an extra include path to the "utility" folder.
+	extraIncludePath *paths.Path
 
 	// The source root for the given origin, where its source files
 	// can be found. Prepending this to SourceFile.RelativePath will give
@@ -61,7 +63,7 @@ func MakeSourceFile(ctx *Context, origin interface{}, path *paths.Path) (*Source
 	case *libraries.Library:
 		res.buildRoot = ctx.LibrariesBuildPath.Join(o.DirName)
 		res.sourceRoot = o.SourceDir
-		res.Library = o
+		res.extraIncludePath = o.UtilityDir
 	default:
 		panic("Unexpected origin for SourceFile: " + fmt.Sprint(origin))
 	}
@@ -77,6 +79,10 @@ func MakeSourceFile(ctx *Context, origin interface{}, path *paths.Path) (*Source
 	return res, nil
 }
 
+func (f *SourceFile) ExtraIncludePath() *paths.Path {
+	return f.extraIncludePath
+}
+
 func (f *SourceFile) SourcePath() *paths.Path {
 	return f.sourceRoot.JoinPath(f.relativePath)
 }