standardize apt-get, rebase to 3.14

Dockerfile

@@ -1,5 +1,5 @@
 ## Buildstage ##
-FROM ghcr.io/linuxserver/baseimage-alpine:3.12 as buildstage
+FROM ghcr.io/linuxserver/baseimage-alpine:3.14 as buildstage
 
 # Build arguments
 ARG VERSION

root/etc/cont-init.d/95-apt-get

@@ -0,0 +1,5 @@
+#!/usr/bin/with-contenv bash
+
+if [ -f /usr/bin/apt ]; then
+    apt-get update
+fi

root/etc/cont-init.d/98-striptracks

@@ -18,7 +18,6 @@ if [ ! -f /usr/bin/mkvmerge ]; then
     if [ -f /usr/bin/apt ]; then
         # Ubuntu
         echo "Installing MKVToolNix using apt-get"
-    apt-get update && \
         apt-get -y install mkvtoolnix && \
         rm -rf /var/lib/apt/lists/*
     elif [ -f /sbin/apk ]; then
@@ -29,7 +28,6 @@ if [ ! -f /usr/bin/mkvmerge ]; then
     else
         # Unknown
         echo "Unknown package manager.  Attempting to install MKVToolNix using apt-get"
-    apt-get update && \
         apt-get -y install mkvtoolnix && \
         rm -rf /var/lib/apt/lists/*
     fi