Separate "launch" into another SourceSet

build.gradle

@@ -46,6 +46,12 @@ compileJava {
     sourceCompatibility = targetCompatibility = '1.8'
 }
 
+sourceSets {
+    launch {
+        compileClasspath += main.compileClasspath + main.runtimeClasspath + main.output
+    }
+}
+
 minecraft {
     version = '1.12.2'
     mappings = 'snapshot_20180731'
@@ -64,7 +70,7 @@ repositories {
 }
 
 dependencies {
-    runtime implementation('org.spongepowered:mixin:0.7.11-SNAPSHOT') {
+    runtime launchCompile('org.spongepowered:mixin:0.7.11-SNAPSHOT') {
         // Mixin includes a lot of dependencies that are too up-to-date
         exclude module: 'launchwrapper'
         exclude module: 'guava'
@@ -79,3 +85,7 @@ mixin {
     defaultObfuscationEnv notch
     add sourceSets.main, 'mixins.baritone.refmap.json'
 }
+
+jar {
+    from sourceSets.launch.output
+}