test: Ignore gdb-pretty-struct-and-enums.rs

Broken on nightly linux distcheck.

Author: brson

src/test/debuginfo/gdb-pretty-struct-and-enums.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// ignore-test also broken on nightly linux distcheck. it's just broken!
 // ignore-windows failing on win32 bot
 // ignore-freebsd: output doesn't match
 // ignore-tidy-linelength