fix the fix (see 278575f)

Author: pehbehbeh

Dockerfile

@@ -59,7 +59,7 @@ RUN apk info \
     && apk del .build-deps
 
 # fix iconv (see https://github.com/docker-library/php/issues/240#issuecomment-305038173)
-RUN apk add --no-cache --repository http://dl-cdn.alpinelinux.org/alpine/edge/community/ 
+RUN apk add --no-cache --repository http://dl-cdn.alpinelinux.org/alpine/edge/testing/ gnu-libiconv
 ENV LD_PRELOAD /usr/lib/preloadable_libiconv.so php
 
 # change default shell