gdb: move debug output inside block in dwarf_record_line_1

gdb: move debug output inside block in dwarf_record_line_1

The debug output that says a line has been recorded is currently
outside the `if` block which decides if the line should be recorded or
not.  This means the debug output will claim the line was recorded,
when actually it wasn't!

Fixed by moving the debug output inside the `if` block.

Should be no user visible changes after this commit (except if debug
output is turned on).

Approved-By: Tom Tromey <tom@tromey.com>