Remove unreleased 2.5-rc-alpine3.6 variant (superseded by the new 2.5-rc-alpine3.7 variant)

See https://github.com/docker-library/official-images/pull/3789#issuecomment-350387112

.travis.yml

@@ -5,7 +5,6 @@ env:
   - VERSION=2.5-rc VARIANT=stretch
   - VERSION=2.5-rc VARIANT=stretch/slim
   - VERSION=2.5-rc VARIANT=alpine3.7
-  - VERSION=2.5-rc VARIANT=alpine3.6
   - VERSION=2.4 VARIANT=stretch
   - VERSION=2.4 VARIANT=stretch/slim
   - VERSION=2.4 VARIANT=jessie

2.5-rc/alpine3.6/Dockerfile

@@ -1,110 +0,0 @@
-FROM alpine:3.6
-
-# skip installing gem documentation
-RUN mkdir -p /usr/local/etc \
-	&& { \
-		echo 'install: --no-document'; \
-		echo 'update: --no-document'; \
-	} >> /usr/local/etc/gemrc
-
-ENV RUBY_MAJOR 2.5-rc
-ENV RUBY_VERSION 2.5.0-preview1
-ENV RUBY_DOWNLOAD_SHA256 c2f518eb04b38bdd562ba5611abd2521248a1608fc466368563dd794ddeddd09
-ENV RUBYGEMS_VERSION 2.7.3
-ENV BUNDLER_VERSION 1.16.0
-
-# some of ruby's build scripts are written in ruby
-#   we purge system ruby later to make sure our final image uses what we just built
-# readline-dev vs libedit-dev: https://bugs.ruby-lang.org/issues/11869 and https://github.com/docker-library/ruby/issues/75
-RUN set -ex \
-	\
-	&& apk add --no-cache --virtual .ruby-builddeps \
-		autoconf \
-		bison \
-		bzip2 \
-		bzip2-dev \
-		ca-certificates \
-		coreutils \
-		dpkg-dev dpkg \
-		gcc \
-		gdbm-dev \
-		glib-dev \
-		libc-dev \
-		libffi-dev \
-		libressl \
-		libressl-dev \
-		libxml2-dev \
-		libxslt-dev \
-		linux-headers \
-		make \
-		ncurses-dev \
-		procps \
-		readline-dev \
-		ruby \
-		tar \
-		xz \
-		yaml-dev \
-		zlib-dev \
-	\
-	&& wget -O ruby.tar.xz "https://cache.ruby-lang.org/pub/ruby/${RUBY_MAJOR%-rc}/ruby-$RUBY_VERSION.tar.xz" \
-	&& echo "$RUBY_DOWNLOAD_SHA256 *ruby.tar.xz" | sha256sum -c - \
-	\
-	&& mkdir -p /usr/src/ruby \
-	&& tar -xJf ruby.tar.xz -C /usr/src/ruby --strip-components=1 \
-	&& rm ruby.tar.xz \
-	\
-	&& cd /usr/src/ruby \
-	\
-# hack in "ENABLE_PATH_CHECK" disabling to suppress:
-#   warning: Insecure world writable dir
-	&& { \
-		echo '#define ENABLE_PATH_CHECK 0'; \
-		echo; \
-		cat file.c; \
-	} > file.c.new \
-	&& mv file.c.new file.c \
-	\
-	&& autoconf \
-	&& gnuArch="$(dpkg-architecture --query DEB_BUILD_GNU_TYPE)" \
-# the configure script does not detect isnan/isinf as macros
-	&& export ac_cv_func_isnan=yes ac_cv_func_isinf=yes \
-	&& ./configure \
-		--build="$gnuArch" \
-		--disable-install-doc \
-		--enable-shared \
-	&& make -j "$(nproc)" \
-	&& make install \
-	\
-	&& runDeps="$( \
-		scanelf --needed --nobanner --format '%n#p' --recursive /usr/local \
-			| tr ',' '\n' \
-			| sort -u \
-			| awk 'system("[ -e /usr/local/lib/" $1 " ]") == 0 { next } { print "so:" $1 }' \
-	)" \
-	&& apk add --virtual .ruby-rundeps $runDeps \
-		bzip2 \
-		ca-certificates \
-		libffi-dev \
-		libressl-dev \
-		procps \
-		yaml-dev \
-		zlib-dev \
-	&& apk del .ruby-builddeps \
-	&& cd / \
-	&& rm -r /usr/src/ruby \
-	\
-	&& gem update --system "$RUBYGEMS_VERSION" \
-	&& gem install bundler --version "$BUNDLER_VERSION" --force
-
-# install things globally, for great justice
-# and don't create ".bundle" in all our apps
-ENV GEM_HOME /usr/local/bundle
-ENV BUNDLE_PATH="$GEM_HOME" \
-	BUNDLE_BIN="$GEM_HOME/bin" \
-	BUNDLE_SILENCE_ROOT_WARNING=1 \
-	BUNDLE_APP_CONFIG="$GEM_HOME"
-ENV PATH $BUNDLE_BIN:$PATH
-RUN mkdir -p "$GEM_HOME" "$BUNDLE_BIN" \
-	&& chmod 777 "$GEM_HOME" "$BUNDLE_BIN"
-
-CMD [ "irb" ]