Fixes:

• Custom ForgeGradle fork is used (this one). Ensures compatibility with Gradle 5.+, fixes some repository references and does a couple obscure manipulations with .classpath file for Eclipse projects to ensure they won't break again;
• Custom maven repository is used for locating all basic dependencies (this one). Since Forge guys keep making breaking changes on their side without caring about old Minecraft versions, this is a much more reliable option than trying to chase their ever-shifting repos;
• Buildscript now enforces Java 8 compliance and UTF-8 encoding for all files.

Building Features:

• Gradle wrapper 5.6.4 is used by default;
• Buildscript contains tasks for generating dev and sources artifacts for your mod, as well as ensures they will be generated alongside main jar when executing gradlew build;
• All data in mcmod.info file is filled when actually building a mod. use gradle.properties file for declaring custom properties used by build.gradle;
• Illustration of how to add another mod to project dependencies, in a form of local file.

Short Setup Guide:

If you ended up here, I assume you are already familiar with how to setup basic Forge workspace, so I won't be covering it all in great detail. Only the most important steps, just in case you forgot something:

1. Ensure you have JDK 8 installed (not just JRE), and JAVA_HOME environment variable is set in your system, pointing to that JDK;
2. Download this repository contents, create folder for your mod-specific workspace and unpack those contents into that folder;
3. Open up a command line in that folder, and execure gradlew setupDecompWorkspace. Once its done, run IDE-specific command to generate project for your IDE; either gradlew eclipse or gradlew idea;
4. In case you use Eclipse, don't forget that you need to open your workspace by choosing eclipse folder within your mod-specific folder as workspace location. In case you use Idea... I dunno, you know better what to do;
5. Use gradlew build whenever you need to build a .jar with your mod. It will end up being in build/libs directory within your mod-specific workspace folder.