Only remap jars when required

src/main/java/net/fabricmc/loom/providers/MinecraftJarProvider.java

@@ -54,6 +54,7 @@ public class MinecraftJarProvider {
 			mergeJars(project);
 		}
 
+		if(!getMappedJar().exists() || !getIntermediaryJar().exists()){
 			if (getMappedJar().exists()) {
 				getMappedJar().delete();
 			}
@@ -61,6 +62,7 @@ public class MinecraftJarProvider {
 				getIntermediaryJar().delete();
 			}
 			new MapJarsTiny().mapJars(this, project);
+		}
 
 		if (!MINECRAFT_MAPPED_JAR.exists()) {
 			throw new RuntimeException("mapped jar not found");