testsuite: Fix recent GCC FAIL: gdb.arch/i386-signal.exp

testsuite: Fix recent GCC FAIL: gdb.arch/i386-signal.exp

gcc-6.2.1-2.fc24.x86_64

(gdb) backtrace 10^M
(gdb) FAIL: gdb.arch/i386-signal.exp: backtrace 10

(gdb) disas/s
Dump of assembler code for function main:
.../gdb/testsuite/gdb.arch/i386-signal.c:
30      {
   0x000000000040057f <+0>:     push   %rbp
   0x0000000000400580 <+1>:     mov    %rsp,%rbp
31        setup ();
   0x0000000000400583 <+4>:     callq  0x400590 <setup>
=> 0x0000000000400588 <+9>:     mov    $0x0,%eax
32      }
   0x000000000040058d <+14>:    pop    %rbp
   0x000000000040058e <+15>:    retq
End of assembler dump.

The .exp patch is an obvious typo fix I think.  The regex was written to
accept "ADDR in main" and I find it OK as checking .debug_line validity is not
the purpose of this testfile.

gcc-4.8.5-11.el7.x86_64 did not put the 'mov $0x0,%eax' instruction there at
all so there was no problem with .debug_line.

gdb/testsuite/ChangeLog
2016-10-05  Jan Kratochvil  <jan.kratochvil@redhat.com>

	* gdb.arch/i386-signal.exp (backtrace 10): Fix #2 typo.