[minor] Don't use savelog to rotate log files

Save log into ${LOG_PATH}/mkiso.log.$(date +%Y%m%d%H%M%S) to simplfy
log parser.

common

@@ -9,7 +9,7 @@
 exit_fail ()
 {
     if [ "$ALL_DONE" == "true" ]; then exit 0; fi
-    echo_and_log "[ERROR] The building process failed, see log file for more details: ${LOG_FILE}.0"
+    echo_and_log "[ERROR] The building process failed, see log file for more details: ${LOG_FILE}"
     clean_up
     exit 1
 }

mkiso

@@ -20,7 +20,6 @@ clean_up ()
 {
     [[ -f "${CHROOT_LOCK}" ]] && postchroot
     [[ -f "${BUILD_LOCK}" ]] && rm ${BUILD_LOCK}
-    savelog -q ${LOG_FILE} 
 }
 
 do_help ()
@@ -130,9 +129,14 @@ script_init ()
 
     APT_ARCHIVE_PATH="${APT_ARCHIVE_BASE}/${VERSION}/${ARCH}"
 
+    ## Don't use savelog to rotate log, instead, save all logs,
+    ## postfix with the log start time
     LOG_PATH="${LOG_BASE}/${VERSION}/${SCHEME}/${ARCH}"
-    LOG_FILE="${LOG_PATH}/${SCRIPT_NAME}.log"
+    LOG_TIME="$(date +%Y%m%d%H%M%S)"
+    LOG_FILE="${LOG_PATH}/${SCRIPT_NAME}.log.${LOG_TIME}"
     [[ -d "${LOG_PATH}" ]] || mkdir -p ${LOG_PATH}
+    ## mkiso.log points to the latest log
+    ln -sf ${SCRIPT_NAME}.log.${LOG_TIME} ${LOG_PATH}/${SCRIPT_NAME}.log
 
     BUILD_LOCK="/tmp/${SCRIPT_NAME}-${VERSION}-${SCHEME}-${ARCH}.lock"
     CHROOT_LOCK="/tmp/${SCRIPT_NAME}-${VERSION}-${SCHEME}-${ARCH}-chroot.lock"
@@ -495,9 +499,8 @@ lockfile ${BUILD_LOCK}
 do_action ${ACTIONS}
 
 echo_and_log "[MKISO] Finished executing actions: ${ACTIONS}"
-echo_and_log "[MKISO] See log for more details: ${LOG_FILE}.0"
+echo_and_log "[MKISO] See log for more details: ${LOG_FILE}"
 
-rm -f ${BUILD_LOCK}
 clean_up
 
 export ALL_DONE="true"