fix(build): Correct location of local curseforge_key.txt file

Relative path bad, use absolute. It causes issues in gradle vers that
have workingDir in caches.

Author: alexytomi

.gitignore

@@ -13,3 +13,4 @@ app_pojavlauncher/.cxx/
 /jre_lwjgl3glfw/gradle/
 /jre_lwjgl3glfw/**/build/
 /jre_lwjgl3glfw/**/.gradle/
+/app_pojavlauncher/curseforge_key.txt

app_pojavlauncher/build.gradle

@@ -54,7 +54,7 @@ def getVersionName = {
 def getCFApiKey = {
     String key = System.getenv("CURSEFORGE_API_KEY");
     if(key != null) return key;
-    File curseforgeKeyFile = new File("./curseforge_key.txt");
+    File curseforgeKeyFile = new File("$projectDir/curseforge_key.txt");
     if(curseforgeKeyFile.canRead() && curseforgeKeyFile.isFile()) {
         return curseforgeKeyFile.text;
     }