Rework gradle, making use of toolchain feature

pgpainless-cli/build.gradle

@@ -4,7 +4,6 @@
 
 plugins {
     id 'application'
-    id "com.github.johnrengelman.shadow" version "6.1.0"
 }
 
 dependencies {
@@ -31,22 +30,6 @@ mainClassName = 'org.pgpainless.cli.PGPainlessCLI'
 application {
     mainClass = mainClassName
 }
-/**
-jar {
-    duplicatesStrategy(DuplicatesStrategy.EXCLUDE)
-    manifest {
-        attributes 'Main-Class': "$mainClassName"
-    }
-
-    from {
-        configurations.runtimeClasspath.collect { it.isDirectory() ? it : zipTree(it) }
-    } {
-        exclude "META-INF/*.SF"
-        exclude "META-INF/*.DSA"
-        exclude "META-INF/*.RSA"
-    }
-}
- */
 
 run {
     // https://stackoverflow.com/questions/59445306/pipe-into-gradle-run
@@ -56,5 +39,3 @@ run {
         args Eval.me(appArgs)
     }
 }
-
-// tasks."jar".dependsOn(":pgpainless-core:assemble", ":pgpainless-sop:assemble")