gradle: Refactor and update to gradle 6

deobfuscator/deobfuscator.gradle.kts

@@ -45,7 +45,7 @@ dependencies {
     implementation(project(":runelite-api"))
     implementation(project(":runescape-api"))
 
-    runtime(Libraries.slf4jSimple)
+    runtimeOnly(Libraries.slf4jSimple)
 
     testImplementation(deobjars)
     testImplementation(Libraries.junit)
@@ -60,22 +60,34 @@ tasks {
     )
 
     processResources  {
+        finalizedBy("filterResources")
+    }
+
+    register<Copy>("filterResources") {
         inputs.properties(tokens)
 
         from("src/main/resources") {
             include("deob.properties")
-
-            filter<ReplaceTokens>("tokens" to tokens)
         }
+        into("${buildDir}/resources/main")
+
+        filter(ReplaceTokens::class, "tokens" to tokens)
+        filteringCharset = "UTF-8"
     }
 
     processTestResources {
+        finalizedBy("filterTestResources")
+    }
+
+    register<Copy>("filterTestResources") {
         inputs.properties(tokens)
 
         from("src/test/resources") {
             include("deob-test.properties")
-
-            filter<ReplaceTokens>("tokens" to tokens)
         }
+        into("${buildDir}/resources/test")
+
+        filter(ReplaceTokens::class, "tokens" to tokens)
+        filteringCharset = "UTF-8"
     }
 }