Add back test for struct initialization

...that had been removed as part of f99bee8103
"Delete OUString UTF-16 string literal ctor/assignment op"

Change-Id: I22423306ab35dcb580ecc90daea3219b6c1578b6
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/159446
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

compilerplugins/clang/test/ostr.cxx

@@ -60,6 +60,9 @@ void f()
     // expected-error-re@+1 {{use a _ustr user-defined string literal instead of constructing an instance of '{{(rtl::)?}}OUString' from an ordinary string literal [loplugin:ostr]}}
     f((("foo")));
 
+    // expected-error-re@+1 {{use a _ustr user-defined string literal instead of constructing an instance of '{{(rtl::)?}}OUString' from an ordinary string literal [loplugin:ostr]}}
+    S s10 = { "foo" };
+
     // Only generate one warning here, not two, for a macro argument used twice in the macro's
     // expansion:
     // expected-error-re@+1 {{use a _ustr user-defined string literal instead of constructing an instance of '{{(rtl::)?}}OUString' from an ordinary string literal [loplugin:ostr]}}