Fix compiler errors due to gradle caching issue.

Author: LexManos

src/mcp/java/net/minecraftforge/gradle/mcp/function/DownloadCoreFunction.java

@@ -36,7 +36,7 @@ class DownloadCoreFunction extends DownloadFileFunction {
     private static DownloadInfo getDownloadInfo(MCPEnvironment environment, String artifact, String extension) {
         try {
             Gson gson = new Gson();
-            Reader reader = new FileReader(environment.getStepOutput(DownloadVersionJSONFunction.class));
+            Reader reader = new FileReader(environment.getStepOutput("downloadManifest"));
             JsonObject json = gson.fromJson(reader, JsonObject.class);
             reader.close();
 

src/mcp/java/net/minecraftforge/gradle/mcp/function/DownloadVersionJSONFunction.java

@@ -40,7 +40,7 @@ public DownloadVersionJSONFunction() {
     private static DownloadInfo getDownloadInfo(MCPEnvironment environment) {
         try {
             Gson gson = new Gson();
-            Reader reader = new FileReader(environment.getStepOutput(DownloadManifestFunction.class));
+            Reader reader = new FileReader(environment.getStepOutput("downloadManifest"));
             JsonObject json = gson.fromJson(reader, JsonObject.class);
             reader.close();
 

src/mcp/java/net/minecraftforge/gradle/mcp/function/ListLibrariesFunction.java

@@ -47,7 +47,7 @@ public File execute(MCPEnvironment environment) {
 
         try {
             Gson gson = new Gson();
-            Reader reader = new FileReader(environment.getStepOutput(DownloadVersionJSONFunction.class));
+            Reader reader = new FileReader(environment.getStepOutput("downloadJson"));
             JsonObject json = gson.fromJson(reader, JsonObject.class);
             reader.close();
 

src/mcp/java/net/minecraftforge/gradle/mcp/util/MCPEnvironment.java

@@ -77,15 +77,6 @@ public File getStepOutput(String name) {
         return step.output;
     }
 
-    public File getStepOutput(Class<? extends MCPFunction> type) {
-        for (MCPRuntime.Step step : runtime.steps.values()) {
-            if (step.isOfType(type)) {
-                return step.output;
-            }
-        }
-        throw new IllegalArgumentException("Could not find a step of type " + type.getName());
-    }
-
     public MinecraftVersion getMinecraftVersion() {
         return this.mcVersion;
     }