[gdb/testsuite] Fix gdb.base/annota1.exp with pie

[gdb/testsuite] Fix gdb.base/annota1.exp with pie

Since commit 359efc2d894 ("[gdb/testsuite] Make gdb.base/annota1.exp more
robust") we see this fail with target board unix/-fPIE/-pie:
...
FAIL: gdb.base/annota1.exp: run until main breakpoint (timeout)
...

The problem is that the commit makes the number and order of matched
annotations fixed, while between target boards unix and unix/-fPIE/-pie there
is a difference:
...
 \032\032post-prompt
 Starting program: outputs/gdb.base/annota1/annota1

+\032\032breakpoints-invalid
+
 \032\032starting

 \032\032frames-invalid
...

Fix this by optionally matching the additional annotation.

Tested on x86_64-linux.