AAPT2: Fix processing of quotes in XML

When processing attributes in XML, quotes can't be used to mark a
section as whitespace preserving, so the assumption should be that the
entire string is whitespace preserving, which makes quote characters
literals.

Bug: 62840718
Bug: 62840406
Test: make aapt2_tests
Change-Id: I4afff02148b5b8e78833abf1f323c2f5325d6155
diff --git a/tools/aapt2/util/Util.h b/tools/aapt2/util/Util.h
index 8bca9dd..410258c 100644
--- a/tools/aapt2/util/Util.h
+++ b/tools/aapt2/util/Util.h
@@ -171,6 +171,8 @@
 
 class StringBuilder {
  public:
+  explicit StringBuilder(bool preserve_spaces = false);
+
   StringBuilder& Append(const android::StringPiece& str);
   const std::string& ToString() const;
   const std::string& Error() const;
@@ -184,6 +186,7 @@
   explicit operator bool() const;
 
  private:
+  bool preserve_spaces_;
   std::string str_;
   size_t utf16_len_ = 0;
   bool quote_ = false;