testsuite: Fix gdb.base/killed-outside.exp using irrelevant stale options

testsuite: Fix gdb.base/killed-outside.exp using irrelevant stale options

Fix a commit 4a556533cf02 ("Fix PR11094: JIT breakpoint is not properly
recreated on reruns") regression:

Running .../gdb/testsuite/gdb.base/killed-outside.exp ...
Executing on host: mips-mti-linux-gnu-gcc  -Wl,--no-as-needed  -c -g  -o .../gdb/testsuite/outputs/gdb.base/killed-outside/killed-outside0.o .../gdb/testsuite/gdb.base/killed-outside.c .../gdb/testsuite/outputs/gdb.base/jit-simple/jit-simple-jit.so    (timeout = 300)
spawn mips-mti-linux-gnu-gcc -Wl,--no-as-needed -c -g -o .../gdb/testsuite/outputs/gdb.base/killed-outside/killed-outside0.o .../gdb/testsuite/gdb.base/killed-outside.c .../gdb/testsuite/outputs/gdb.base/jit-simple/jit-simple-jit.so
mips-mti-linux-gnu-gcc: warning: .../gdb/testsuite/outputs/gdb.base/jit-simple/jit-simple-jit.so: linker input file unused because linking not done
output is:
mips-mti-linux-gnu-gcc: warning: .../gdb/testsuite/outputs/gdb.base/jit-simple/jit-simple-jit.so: linker input file unused because linking not done

gdb compile failed, mips-mti-linux-gnu-gcc: warning: .../gdb/testsuite/outputs/gdb.base/jit-simple/jit-simple-jit.so: linker input file unused because linking not done
UNTESTED: gdb.base/killed-outside.exp: failed to prepare

and adjust the call to `prepare_for_testing' by removing a reference to
`options', which is not set in this test case but a stale value is
carried over from `gdb.base/jit-simple.exp' previously executed in a
full test suite run.

	gdb/testsuite/
	* gdb.base/killed-outside.exp: Remove $options from a call to
	`prepare_for_testing'.