Improved readability of multilib parse-config replacing 'expr' and backtick notation

lib/multilib/parse-config

@@ -35,10 +35,11 @@ multilib_abi_loop() {
 	esac
 
 	# alter arch_target if we build 32bit
-	if expr $abi : "32" > /dev/null ; then
-		arch_target="`echo $arch_target | arch2arch32`"
+	if [ "$abi" = "32" ]; then
+		arch_target="$( echo $arch_target | arch2arch32 )"
 		echo_status "Setting arch_target to $arch_target"
 	fi
+
 	# set a proper arch_suffix for pkggetdir to set the right libdir
 	arch_suffix=$abi
 	set_confopt