At least on debina 12.5, with GDB 13.1 and GDB 14.1, 2 gdbserver tests
fails due to a 'warning: ' word appearing in from of a line
giving the syscall-template.S filename.
Fix this by allowing an optional 'warning: ' regexp at the beginning of the line.
Tested on debian 12.5, with GDB 12.1/13.1/14.1 and 15.0.50.
20240211-git
/^[ ]*at \.\.\/sysdeps\/unix\/syscall-template\.S/d
/^[ ]*in \.\.\/sysdeps\/unix\/syscall-template\.S/d
-/^[1-9][0-9]*[ ]*\.\.\/sysdeps\/unix\/syscall-template\.S/d
+/^\(warning: \)\?[1-9][0-9]*[ ]*\.\.\/sysdeps\/unix\/syscall-template\.S/d
/^[1-9][0-9]*[ ]in *\.\.\/sysdeps\/unix\/syscall-template\.S/d
/^[1-9][0-9]*[ ]T_PSEUDO (SYSCALL_SYMBOL, SYSCALL_NAME, SYSCALL_NARGS)/d