Issue Description:

I am unable to compile EnderIO from source.

What happens:

I receive an error about failure to locate the deobfuscated version of EnderCore.

What you expected to happen:

Compilation should succeed.

Steps to reproduce:

1. git clone https://github.com/SleepyTrousers/EnderIO
2. cd EnderIO
3. ./gradlew setupDecompWorkspace
4. ./gradlew build

Affected Versions (Do not use "latest"):

• EnderIO: 9249b7e
• EnderCore: 0.5.76
• Minecraft: 1.12.2
• Forge: 14.23.5.2847
• SpongeForge? N/A
• Optifine? N/A
• Single Player and/or Server? N/A

Your most recent log file where the issue was present:

I removed several of the repeated warnings about FG 5 and the mappings.

> Configure project : 
This mapping 'snapshot_20171212' was designed for MC 1.12! Use at your own peril.
This mapping 'snapshot_20171212' was designed for MC 1.12! Use at your own peril.
WARNING: You are using an unsupported version of ForgeGradle.
Please consider upgrading to ForgeGradle 5 and helping in the efforts to get old versions working on the modern toolchain.
See https://gist.github.com/TheCurle/fe7ad3ede188cbdd15c235cc75d52d4a for more info on contributing.

> Configure project :enderio-integration-thaumcraft 
WARNING: You are using an unsupported version of ForgeGradle.
Please consider upgrading to ForgeGradle 5 and helping in the efforts to get old versions working on the modern toolchain.
See https://gist.github.com/TheCurle/fe7ad3ede188cbdd15c235cc75d52d4a for more info on contributing.

FAILURE: Build failed with an exception.

* What went wrong:
Could not resolve all files for configuration ':ap:compileClasspath'.
> Could not find EnderCore.jar (deobf.com.enderio.core:EnderCore:1.12.2-0.5.76).
  Searched in the following locations:
      http://files.minecraftforge.net/maven/deobf/com/enderio/core/EnderCore/1.12.2-0.5.76/EnderCore-1.12.2-0.5.76.jar

* Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.

* Get more help at https://help.gradle.org

BUILD FAILED in 3s
5 actionable tasks: 3 executed, 2 up-to-date

According to your build.gradle you are still using ForgeGradle 2.3:

https://github.com/SleepyTrousers/EnderIO/blob/9249b7e01fd73c7bc92a2fd60e768c1ef5b39fd3/build.gradle#L14

As far as I know, the newer versions of Forge require ForgeGradle 3.

I should note that I am also able to compile other Forge 2847 mods like More Refined Storage without issue.

oh your using outdated forge version use 2854 see if this still exist

EnderCore is not included by default. You need to place the EnderCore file from our maven into the "libs" folder, or include it as a dependency in build.gradle. Somewhere is a guide on how to properly setup the workspace, but I can't find it now. That's the way I set it up for myself

Maven is https://maven.tterrag.com

Also just curious, why are you wanting to compile it yourself? We have dev builds for everything that gets comitted here. If you are wanting to help port it, then you should really join our discord so you can co-ordinate with everyone else already working on porting

EnderCore is not included by default. You need to place the EnderCore file from our maven into the "libs" folder, or include it as a dependency in build.gradle.

Thanks. That was the step I had missed.

(The Forge Maven URL also needs to be adjusted; I'll send a PR for that.)

Also just curious, why are you wanting to compile it yourself?

I still use 1.12, mainly for performance reasons; the newer renderer is a lot slower even with Sodium/other performance mods. As such, I'm often needing to patch various issues in mods. Most of the time I just use mixins, as only a few developers are willing to accept fixes for 1.12, even if community-contributed. EnderIO appears to still be somewhat maintained for 1.12, so I'd rather provide a direct fix upstream than use mixins.