Handle the case /etc/hostid is being wrongly marked as conffile

There are packages distributed with /etc/hostid file installed as conffile,
which is going to cause problem when the package is purged. Here we detect
such case and migrate it to an ordinary file that preserves during purge.

Also replace the endianness detection code to use od(1) from coreutils
instead of requiring gcc

debian/spl.postinst

@@ -21,6 +21,12 @@ set -e
 # If this file don't already exists on our system or has less than 4 bytes, then
 # we will stabilize our current hostid by writing its value to /etc/hostid
 
+# Detect if /etc/hostid is a conffile of previous spl package, migrate if yes
+# hostid file should preserve even when package is purged
+if $(dpkg-query --showformat='${Conffiles}\n' --show spl >/dev/null 2>&1); then
+	dpkg-maintscript-helper rm_conffile /etc/hostid -- "$@"
+fi
+
 if [ ! -f /etc/hostid ] || [ $(stat -c %s /etc/hostid) -lt 4 ] ; then
 
 	# Write our current hostid to /etc/hostid
@@ -31,7 +37,7 @@ if [ ! -f /etc/hostid ] || [ $(stat -c %s /etc/hostid) -lt 4 ] ; then
 	DD=$(echo $HOSTID | cut -b 7,8)
 
 	# Big Endian
-	if echo | gcc -E -dM - | grep -q "__BYTE_ORDER__.*__ORDER_BIG_ENDIAN__"; then
+	if [ $(echo -n I | od -to2 | awk 'FNR==1{ print substr($2,6,1)}' 2>/dev/null) = 0 ]; then
 		# Invoke the printf from coreutils. shell builtin lacks the byte format.
 		/usr/bin/printf "\x$AA\x$BB\x$CC\x$DD" >/etc/hostid
 	else

debian/spl.postrm

@@ -0,0 +1,10 @@
+#!/bin/sh
+set -e
+
+# Detect if /etc/hostid is a conffile of previous spl package, migrate if yes
+# hostid file should preserve even when package is purged
+if $(dpkg-query --showformat='${Conffiles}\n' --show spl >/dev/null 2>&1); then
+        dpkg-maintscript-helper rm_conffile /etc/hostid -- "$@"
+fi
+
+#DEBHELPER#

debian/spl.preinst

@@ -0,0 +1,10 @@
+#!/bin/sh
+set -e
+
+# Detect if /etc/hostid is a conffile of previous spl package, migrate if yes
+# hostid file should preserve even when package is purged
+if $(dpkg-query --showformat='${Conffiles}\n' --show spl >/dev/null 2>&1); then
+        dpkg-maintscript-helper rm_conffile /etc/hostid -- "$@"
+fi
+
+#DEBHELPER#