network/fail2ban: Misc automated cleanups.

Signed-off-by: David Somero <xgizzmo@slackbuilds.org>

network/fail2ban/fail2ban.SlackBuild

@@ -26,16 +26,24 @@
 
 PRGNAM=fail2ban
 VERSION=0.8.4
-ARCH=${ARCH:-i486}
 BUILD=${BUILD:-1}
 TAG=${TAG:-_SBo}
 
+# Automatically determine the architecture we're building on:
+if [ -z "$ARCH" ]; then
+  case "$( uname -m )" in
+    i?86) ARCH=i486 ;;
+    arm*) ARCH=arm ;;
+    # Unless $ARCH is already set, use uname -m for all other archs:
+       *) ARCH=$( uname -m ) ;;
+  esac
+fi
+
+CWD=$(pwd)
 TMP=${TMP:-/tmp/SBo}
 PKG=$TMP/package-$PRGNAM
 OUTPUT=${OUTPUT:-/tmp}
-CWD=$(pwd)
 
-# exit on most errors
 set -e
 
 # clean up from previous builds