cli: Use dedicated shadow plugin for building fat jar

'gradle shadowJar' can be used to build a fat jar
'gradle jar' now only builds slim jar

pgpainless-cli/README.md

@@ -13,14 +13,14 @@ PGPainless-CLI is an implementation of the [Stateless OpenPGP Command Line Inter
 It plugs `pgpainless-sop` into `sop-java-picocli`.
 
 ## Build
-To build an executable, `gradle jar` should be sufficient. The resulting jar file can be found in `pgpainless-sop/build/libs/`.
+To build an executable, `gradle shadowJar` should be sufficient. The resulting jar file can be found in `pgpainless-cli/build/libs/`.
 
 ## Execute
 
 The jar file produced in the step above is executable as is.
 
 ```
-java -jar pgpainless-cli-XXX.jar help
+java -jar pgpainless-cli-XXX-all.jar help
 ```
 
 Alternatively you can use the provided `./pgpainless-cli` script to directly build and execute PGPainless' Stateless Command Line Interface from within Gradle.

pgpainless-cli/build.gradle

@@ -4,6 +4,7 @@
 
 plugins {
     id 'application'
+    id "com.github.johnrengelman.shadow" version "6.1.0"
 }
 def generatedVersionDir = "${buildDir}/generated-version"
 
@@ -51,7 +52,7 @@ mainClassName = 'org.pgpainless.cli.PGPainlessCLI'
 application {
     mainClass = mainClassName
 }
-
+/**
 jar {
     duplicatesStrategy(DuplicatesStrategy.EXCLUDE)
     manifest {
@@ -66,6 +67,7 @@ jar {
         exclude "META-INF/*.RSA"
     }
 }
+ */
 
 run {
     // https://stackoverflow.com/questions/59445306/pipe-into-gradle-run
@@ -76,4 +78,4 @@ run {
     }
 }
 
-tasks."jar".dependsOn(":pgpainless-core:assemble", ":pgpainless-sop:assemble")
+// tasks."jar".dependsOn(":pgpainless-core:assemble", ":pgpainless-sop:assemble")