Add test for 'invalid literal for int()' exception in gdb pretty-printers

src/test/debuginfo/pretty-std.rs

@@ -38,6 +38,9 @@
 // gdbg-check:$6 = None
 // gdbr-check:$6 = core::option::Option::None
 
+// gdb-command: print some_string
+// gdbr-check:$7 = Some = {"IAMA optional string!"}
+
 
 // === LLDB TESTS ==================================================================================
 
@@ -82,6 +85,8 @@ fn main() {
     let some = Some(8i16);
     let none: Option<i64> = None;
 
+    let some_string = Some("IAMA optional string!".to_owned());
+
     zzz(); // #break
 }