unixodbc: auto-generate odbcinst.ini

This allows ODBC drivers to create odbcinst.ini-snippets in
/etc/odbcinst.ini.d/ which will be assembled into
/tmp/etc/odbcinst.ini. /etc/odbcinst.ini is provided as a symlink
pointing to /tmp/etc/odbcinst.ini
Hence the unixODBC-provided PostgreSQL driver was also given an
odbcinst.ini.d snippet.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

libs/unixodbc/files/odbc.init

@@ -0,0 +1,26 @@
+#!/bin/sh /etc/rc.common
+
+START=50
+
+gen_odbcinst() {
+	local inifile
+
+	echo "[ODBC]"
+	echo "Trace = off"
+	echo "TraceFile ="
+
+	for inifile in /etc/odbcinst.ini.d/*.ini; do
+		cat "$inifile"
+	done
+}
+
+start() {
+	[ ! -d /tmp/etc ] && mkdir /tmp/etc
+
+	gen_odbcinst > /tmp/etc/odbcinst.ini.new
+	chmod 0644 /tmp/etc/odbcinst.ini.new
+
+	[ -e /tmp/etc/odbcinst.ini ] && ( rm /tmp/etc/odbcinst.ini || return 1 )
+
+	mv /tmp/etc/odbcinst.ini.new /tmp/etc/odbcinst.ini
+}