Product config makefiles to Starlark converter

Test: treehugger; internal tests in mk2rbc_test.go
Bug: 172923994
Change-Id: I43120b9c181ef2b8d9453e743233811b0fec268b

androidmk/parser/parser.go

@@ -216,13 +216,14 @@ func (p *parser) parseDirective() bool {
 		// Nothing
 	case "else":
 		p.ignoreSpaces()
-		if p.tok != '\n' {
+		if p.tok != '\n' && p.tok != '#' {
 			d = p.scanner.TokenText()
 			p.accept(scanner.Ident)
 			if d == "ifdef" || d == "ifndef" || d == "ifeq" || d == "ifneq" {
 				d = "el" + d
 				p.ignoreSpaces()
 				expression = p.parseExpression()
+				expression.TrimRightSpaces()
 			} else {
 				p.errorf("expected ifdef/ifndef/ifeq/ifneq, found %s", d)
 			}