board/qemu: fix post-image

Last-minute changes to d9b244d8a3 (board/qemu: define start qemu
script outside of post-image script) were not tested before being
pushed, so they introduced a bug.

As Arnout put it:
    [...] multiple expressions need a -e to interpret them as
    expressions (now they're interpreted as file names).

Fixes: d9b244d8a3

Reported-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Cc: James Knight <james.d.knight@live.com>

board/qemu/post-image.sh

@@ -41,10 +41,10 @@ case ${DEFCONFIG_NAME} in
     ;;
 esac
 
-sed "s|@SERIAL_ARGS@|${SERIAL_ARGS}|g" \
-    "s|@DEFAULT_ARGS@|${DEFAULT_ARGS}|g" \
-    "s|@QEMU_CMD_LINE@|${QEMU_CMD_LINE}|g" \
-    "s|@HOST_DIR@|${HOST_DIR}|g" \
+sed -e "s|@SERIAL_ARGS@|${SERIAL_ARGS}|g" \
+    -e "s|@DEFAULT_ARGS@|${DEFAULT_ARGS}|g" \
+    -e "s|@QEMU_CMD_LINE@|${QEMU_CMD_LINE}|g" \
+    -e "s|@HOST_DIR@|${HOST_DIR}|g" \
     <"${QEMU_BOARD_DIR}/start-qemu.sh.in" \
     >"${START_QEMU_SCRIPT}"
 chmod +x "${START_QEMU_SCRIPT}"