dut-console: add the missing quotation mark

Add the missing quotation mark in help message.

The help message was:
${CROSS_ARCH}-gdb \
        /build/${BOARD}/usr/lib/debug/boot/vmlinux \
        -ex "target remote $(cat /tmp/kdmx_cpu_9001_gdb)
                                                        ^
                                               not closed

BUG=None
TEST=dut-console -c cpu -p 9001 -k

Change-Id: Idfa55858cb4914fe832d4f7f9d78ef9d14297c01
Signed-off-by: Tzung-Bi Shih <tzungbi@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/1725378
Reviewed-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-by: Aseda Aboagye <aaboagye@chromium.org>
Commit-Queue: Nicolas Boichat <drinkcat@chromium.org>
diff --git a/contrib/dut-console b/contrib/dut-console
index 57e709c..8706464 100755
--- a/contrib/dut-console
+++ b/contrib/dut-console
@@ -147,7 +147,7 @@
     echo "You can now use kdbg inside the chroot with a command like:"
     echo '${CROSS_ARCH}-gdb \
         /build/${BOARD}/usr/lib/debug/boot/vmlinux \
-        -ex "target remote $(cat '"${spath_in}"'_gdb)'
+        -ex "target remote $(cat '"${spath_in}"'_gdb)"'
   fi
 
   echo "Opening ${pty_name}:${pty}..."