AAPT2: Proguard rules generation added.

Change-Id: Ifbe79516cd9a1ade471e211a259301c63b62ac67
diff --git a/tools/aapt2/Source.h b/tools/aapt2/Source.h
index 10c75aa..3606488 100644
--- a/tools/aapt2/Source.h
+++ b/tools/aapt2/Source.h
@@ -19,6 +19,7 @@
 
 #include <ostream>
 #include <string>
+#include <tuple>
 
 namespace aapt {
 
@@ -80,6 +81,10 @@
     return out << source.path << ":" << source.line << ":" << source.column;
 }
 
+inline bool operator<(const SourceLine& lhs, const SourceLine& rhs) {
+    return std::tie(lhs.path, lhs.line) < std::tie(rhs.path, rhs.line);
+}
+
 } // namespace aapt
 
 #endif // AAPT_SOURCE_H