Fix tests for Gradle 6.x

Author: jjohannes

src/test/groovy/org/gradlex/jvm/dependency/conflict/test/CapabilityWithDifferentVersionsTest.groovy

@@ -3,6 +3,8 @@ package org.gradlex.jvm.dependency.conflict.test
 import org.gradlex.jvm.dependency.conflict.test.fixture.GradleBuild
 import spock.lang.Specification
 
+import static org.gradlex.jvm.dependency.conflict.test.fixture.GradleBuild.GRADLE6_TEST
+
 class CapabilityWithDifferentVersionsTest extends Specification {
 
     @Delegate
@@ -37,6 +39,7 @@ class CapabilityWithDifferentVersionsTest extends Specification {
                 println(configurations.compileClasspath.get().files.joinToString("\\n") { it.name })
             }
         """
+        if (GRADLE6_TEST) { configureEnvAttribute() }
 
         expect:
         printJars()
@@ -50,7 +53,7 @@ class CapabilityWithDifferentVersionsTest extends Specification {
                 id("java-library")
             }
             tasks.withType<JavaCompile>().configureEach {
-                options.release = 17
+                options.release.set(17)
             }
             repositories.mavenCentral()
             dependencies {
@@ -62,8 +65,18 @@ class CapabilityWithDifferentVersionsTest extends Specification {
                 println(configurations.compileClasspath.get().files.joinToString("\\n") { it.name })
             }
         """
+        if (GRADLE6_TEST) { configureEnvAttribute() }
 
         expect:
         printJars()
     }
+
+    void configureEnvAttribute() {
+        buildFile << """
+            val envAttribute = Attribute.of("org.gradle.jvm.environment", String::class.java)
+            configurations.compileClasspath {
+                attributes.attribute(envAttribute, "standard-jvm")
+            }
+        """
+    }
 }