Fix a commit f90183d7e3 ("Get GDBserver pid on remote target") bug and
correctly handle the case where the PID of `gdbserver' could not have
been retrieved. If that happens, $server_pid is unset causing:
FAIL: gdb.server/server-kill.exp: p server_pid
ERROR: tcl error sourcing .../gdb/testsuite/gdb.server/server-kill.exp.
ERROR: can't read "server_pid": no such variable
while executing
"if {$server_pid == "" } {
return -1
}"
(file ".../gdb/testsuite/gdb.server/server-kill.exp" line 49)
invoked from within
"source .../gdb/testsuite/gdb.server/server-kill.exp"
("uplevel" body line 1)
invoked from within
"uplevel #0 source .../gdb/testsuite/gdb.server/server-kill.exp"
invoked from within
"catch "uplevel #0 source $test_file_name""
Verify that the variable exists then rather than trying to access it.
gdb/testsuite/
* gdb.server/server-kill.exp: Verify whether `server_pid' exists
rather then trying to access it in determining whether the PID
of `gdbserver' could have been retrieved.
0726fcc61a