resolve iconv issue (see docker-library/php#1121)

Author: phoenix-bjoern

Dockerfile

@@ -10,6 +10,10 @@ ENV RELAYHOST_PASSWORD=
 # (optional) Should the postfix relay use TLS
 ENV SMTP_USE_TLS=
 
+# Fixes an bug with iconv @see https://github.com/docker-library/php/issues/240
+RUN apk add --no-cache --repository http://dl-cdn.alpinelinux.org/alpine/v3.13/community/ gnu-libiconv==1.15-r3
+ENV LD_PRELOAD /usr/lib/preloadable_libiconv.so php
+
 RUN apk --no-cache --repository=http://dl-cdn.alpinelinux.org/alpine/edge/testing/ add \
         ca-certificates \
         gettext \