common: post-build.sh: Avoid duping fstab entries in dirty build

Delete the old entries with the same mountpoint.

Change-Id: I3b898f0ad3ee28a12f6262725ab233387050f0bf
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>

common/post-build.sh

@@ -35,7 +35,7 @@ function fixup_part()
 	FS_TYPE=${3:-auto}
 	OPT=${4:-defaults}
 
-	sed -i "#[[:space:]]${MOUNT}[[:space:]]#d" ${TARGET_DIR}/etc/fstab
+	sed -i "/[[:space:]]${MOUNT//\//\\\/}[[:space:]]/d" ${TARGET_DIR}/etc/fstab
 
 	echo -e "${DEV}\t${MOUNT}\t${FS_TYPE}\t${OPT}\t0 2" >> \
 		${TARGET_DIR}/etc/fstab