Disable log4j jansi support when compiling, removes a warning about it.

src/main/java/net/fabricmc/loom/configuration/CompileConfiguration.java

@@ -262,6 +262,7 @@ public final class CompileConfiguration {
 			// Disable some things used by log4j via the mixin AP that prevent it from being garbage collected
 			System.setProperty("log4j2.disable.jmx", "true");
 			System.setProperty("log4j.shutdownHookEnabled", "false");
+			System.setProperty("log4j.skipJansi", "true");
 
 			project.getLogger().info("Configuring compiler arguments for Java");
 			new JavaApInvoker(project).configureMixin();