ignore more gdb versions with buggy rust support
This extends the versions of gdb which were ignored in #39039. While just ignoring gdb versions up to 7.12.1 would have been sufficient for now, I believe (after consulting https://sourceware.org/gdb/wiki/Internals%20Versions) that ignoring versions up to 7.12.9 will prevent the tests failing again for 7.12.2, etc. while still running all tests for the development versions of gdb (which will be >= 7.12.10 as far as I can tell).
This should fix#39522.
cc @Manishearth, @michaelwoerister, #38948
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