Grimoire compatibility patch. Fixes #1.

src/main/java/com/falsepattern/endlessids/mixin/plugin/MixinPlugin.java

@@ -77,6 +77,8 @@ public class MixinPlugin implements IMixinConfigPlugin {
         return mixins;
     }
 
+    private int grimoireDetected = -1;
+
     private boolean loadJarOf(final TargetedMod mod) {
         try {
             val jar = findJarOf(mod);
@@ -86,10 +88,22 @@ public class MixinPlugin implements IMixinConfigPlugin {
             }
 
             LOG.info("Attempting to add " + jar + " to the URL Class Path");
-            if(!jar.exists()) {
+            if (!jar.exists()) {
                 throw new FileNotFoundException(jar.toString());
             }
-            MinecraftURLClassPath.addJar(jar);
+            if (grimoireDetected < 0) {
+                try {
+                    Class.forName("io.github.crucible.grimoire.Grimoire", false, getClass().getClassLoader());
+                    grimoireDetected = 1;
+                } catch (ClassNotFoundException ignored) {
+                    grimoireDetected = 0;
+                }
+            }
+            if (grimoireDetected == 1) {
+                LOG.info("Not adding " + jar + " to the URL Class Path, because Grimoire breaks our utility class.");
+            } else {
+                MinecraftURLClassPath.addJar(jar);
+            }
             return true;
         }
         catch (Exception e) {