pdf2svg docker build fails with 'aclocal-1.15' is not found error

fixed dockerfile
```
FROM alpine:3.6 as builder
LABEL version="0.2.3-alpine3.6"

RUN apk add --update-cache make gcc libc-dev cairo-dev poppler-dev git autoconf automake libtool

ENV PDF2SVG_VERSION v0.2.3

RUN git clone https://github.com/dawbarton/pdf2svg pdf2svg

WORKDIR /pdf2svg

RUN git checkout $PDF2SVG_VERSION && autoreconf -f -i && ./configure && make

# final image
FROM alpine:3.6

RUN apk add --update-cache --virtual .fetch-deps ca-certificates openssl \
&& update-ca-certificates \
&& apk add --no-cache poppler-glib poppler-utils msttcorefonts-installer \
&& update-ms-fonts \
&& fc-cache -f

RUN apk del .fetch-deps

COPY --from=builder /pdf2svg/pdf2svg /usr/local/bin/pdf2svg
CMD ["pdf2svg"]
```