rename mkiso to mkalpine

this is just a wrapper script. the real stuff happens in alpine.mk

mkalpine

+#!/bin/sh
+
+# first look for alpine.mk in current dir. Fallback to /usr/share/abuild
+mk=./alpine.mk
+if ! [ -f $mk ]; then
+	mk=/usr/share/abuild/alpine.mk
+fi
+
+make -f "$mk" APK_BIN= $@

mkiso

-#!/bin/sh
-
-make -f alpine.mk