AAPT2: Do not interpret %n as a format specifier in string resources

%n is a special value marking a platform independent newline and is
not to be considered a format argument.

Bug: 37132275
Test: make aapt2_tests
Change-Id: I806521e44afe20004344dee9f18ecee6cc7086ea

tools/aapt2/ResourceParser_test.cpp

@@ -843,4 +843,9 @@ TEST_F(ResourceParserTest, ParseElementWithNoValue) {
   EXPECT_THAT(*str->value, Eq(""));
 }
 
+TEST_F(ResourceParserTest, ParsePlatformIndependentNewline) {
+  std::string input = R"(<string name="foo">%1$s %n %2$s</string>)";
+  ASSERT_TRUE(TestParse(input));
+}
+
 }  // namespace aapt

tools/aapt2/util/Util.cpp

@@ -203,7 +203,7 @@ bool VerifyJavaStringFormat(const StringPiece& str) {
     if (*c == '%' && c + 1 < end) {
       c++;
 
-      if (*c == '%') {
+      if (*c == '%' || *c == 'n') {
         c++;
         continue;
       }