Manually declare the fatjar as requiring Java 17

For some reason, the ShadowJar plugin doesn't automatically use the same
JVM version attribute from the Jar task. This can lead to consumers
accidentally resolving the fat-jar instead of the main jar if their
language version is incorrectly set or behaving weirdly. Working around
this by manually specifying J17 in the shadowRuntimeElements
configuration.

Author: Jonathing

build.gradle

@@ -1,3 +1,4 @@
+import org.gradle.api.attributes.java.TargetJvmVersion
 import com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar
 
 plugins {
@@ -23,6 +24,12 @@ java {
 }
 
 configurations {
+    named('shadowRuntimeElements') {
+        attributes {
+            attribute TargetJvmVersion.TARGET_JVM_VERSION_ATTRIBUTE, 17
+        }
+    }
+
     resolvable('shadowOnly') {
         description = 'Implementation dependencies that are not declared as required dependencies.'
     }