Fix MSSQL issue with a non-installed dependency

php-fpm/Dockerfile-72

@@ -325,7 +325,7 @@ RUN if [ ${INSTALL_MSSQL} = true ]; then \
     # Ref from https://github.com/Microsoft/msphpsql/wiki/Dockerfile-for-adding-pdo_sqlsrv-and-sqlsrv-to-official-php-image
     #####################################
     # Add Microsoft repo for Microsoft ODBC Driver 13 for Linux
-    apt-get update -yqq && apt-get install -y apt-transport-https \
+    apt-get update -yqq && apt-get install -y apt-transport-https gnupg \
         && curl https://packages.microsoft.com/keys/microsoft.asc | apt-key add - \
         && curl https://packages.microsoft.com/config/debian/8/prod.list > /etc/apt/sources.list.d/mssql-release.list \
         && apt-get update -yqq \