remove unnecessary env commands

These environment variables are not needed since they are only being used at build time and we are already specifying them using the ARG command, no need to specify it twice since it increases build time and size.

php-fpm/Dockerfile-70

@@ -41,7 +41,6 @@ MAINTAINER Mahmoud Zalt <mahmoud@zalt.me>
 #####################################
 
 ARG INSTALL_XDEBUG=true
-ENV INSTALL_XDEBUG ${INSTALL_XDEBUG}
 RUN if [ ${INSTALL_XDEBUG} = true ]; then \
     # Install the xdebug extension
     pecl install xdebug && \
@@ -56,7 +55,6 @@ COPY ./xdebug.ini /usr/local/etc/php/conf.d/xdebug.ini
 #####################################
 
 ARG INSTALL_MONGO=true
-ENV INSTALL_MONGO ${INSTALL_MONGO}
 RUN if [ ${INSTALL_MONGO} = true ]; then \
     # Install the mongodb extension
     pecl install mongodb && \
@@ -68,7 +66,6 @@ RUN if [ ${INSTALL_MONGO} = true ]; then \
 #####################################
 
 ARG INSTALL_ZIP_ARCHIVE=true
-ENV INSTALL_ZIP_ARCHIVE ${INSTALL_ZIP_ARCHIVE}
 RUN if [ ${INSTALL_ZIP_ARCHIVE} = true ]; then \
     # Install the zip extension
     pecl install zip && \
@@ -80,7 +77,6 @@ RUN if [ ${INSTALL_ZIP_ARCHIVE} = true ]; then \
 #####################################
 
 ARG INSTALL_MEMCACHED=true
-ENV INSTALL_MEMCACHED ${INSTALL_MEMCACHED}
 RUN if [ ${INSTALL_MEMCACHED} = true ]; then \
     # Install the php memcached extension
     curl -L -o /tmp/memcached.tar.gz "https://github.com/php-memcached-dev/php-memcached/archive/php7.tar.gz" \
@@ -102,7 +98,6 @@ RUN if [ ${INSTALL_MEMCACHED} = true ]; then \
 # Opcache:
 #####################################
 ARG INSTALL_OPCACHE=true
-ENV INSTALL_OPCACHE ${INSTALL_OPCACHE}
 RUN if [ ${INSTALL_OPCACHE} = true ]; then \
     docker-php-ext-install opcache && \
     docker-php-ext-enable opcache \