Use precompiled PHP extensions for docker container

This should hopefully reduce the build times for cross compiled images, as we dont have to build extensions from source there.

.docker/apache2-foreground

@@ -0,0 +1,43 @@
+#!/bin/bash
+
+### Taken from here: https://github.com/docker-library/php/blob/master/apache2-foreground
+
+set -e
+
+# Note: we don't just use "apache2ctl" here because it itself is just a shell-script wrapper around apache2 which provides extra functionality like "apache2ctl start" for launching apache2 in the background.
+# (also, when run as "apache2ctl <apache args>", it does not use "exec", which leaves an undesirable resident shell process)
+
+: "${APACHE_CONFDIR:=/etc/apache2}"
+: "${APACHE_ENVVARS:=$APACHE_CONFDIR/envvars}"
+if test -f "$APACHE_ENVVARS"; then
+	. "$APACHE_ENVVARS"
+fi
+
+# Apache gets grumpy about PID files pre-existing
+: "${APACHE_RUN_DIR:=/var/run/apache2}"
+: "${APACHE_PID_FILE:=$APACHE_RUN_DIR/apache2.pid}"
+rm -f "$APACHE_PID_FILE"
+
+# create missing directories
+# (especially APACHE_RUN_DIR, APACHE_LOCK_DIR, and APACHE_LOG_DIR)
+for e in "${!APACHE_@}"; do
+	if [[ "$e" == *_DIR ]] && [[ "${!e}" == /* ]]; then
+		# handle "/var/lock" being a symlink to "/run/lock", but "/run/lock" not existing beforehand, so "/var/lock/something" fails to mkdir
+		#   mkdir: cannot create directory '/var/lock': File exists
+		dir="${!e}"
+		while [ "$dir" != "$(dirname "$dir")" ]; do
+			dir="$(dirname "$dir")"
+			if [ -d "$dir" ]; then
+				break
+			fi
+			absDir="$(readlink -f "$dir" 2>/dev/null || :)"
+			if [ -n "$absDir" ]; then
+				mkdir -p "$absDir"
+			fi
+		done
+
+		mkdir -p "${!e}"
+	fi
+done
+
+exec apache2 -DFOREGROUND "$@"