AAPT2: allow regexes for extensions to not compress

Change-Id: I09d2ad1d1466643ca7628c6480224e16b9002ee5
Fixes: 67575899
Test: added + manual
diff --git a/tools/aapt2/cmd/Util.cpp b/tools/aapt2/cmd/Util.cpp
index 792120e..e2c65ba7 100644
--- a/tools/aapt2/cmd/Util.cpp
+++ b/tools/aapt2/cmd/Util.cpp
@@ -435,4 +435,11 @@
   }
 }
 
+std::regex GetRegularExpression(const std::string &input) {
+  // Standard ECMAScript grammar plus case insensitive.
+  std::regex case_insensitive(
+      input, std::regex_constants::icase | std::regex_constants::ECMAScript);
+  return case_insensitive;
+}
+
 }  // namespace aapt