Product config makefiles to Starlark converter

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

androidmk/parser/make_strings.go

@@ -278,6 +278,15 @@ func (ms *MakeString) ReplaceLiteral(input string, output string) {
 	}
 }
 
+// If MakeString is $(var) after trimming, returns var
+func (ms *MakeString) SingleVariable() (*MakeString, bool) {
+	if len(ms.Strings) != 2 || strings.TrimSpace(ms.Strings[0]) != "" ||
+		strings.TrimSpace(ms.Strings[1]) != "" {
+		return nil, false
+	}
+	return ms.Variables[0].Name, true
+}
+
 func splitAnyN(s, sep string, n int) []string {
 	ret := []string{}
 	for n == -1 || n > 1 {

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)
 			}