feat(gradle-inspector): Allow to customize the Java home for analysis

Note that `setJavaHome()` [1] sets the Java home "to use for the Gradle
process". However, as by default (unless toolchains are used [2]) "Gradle
will compile Java code to the language level of the JVM running Gradle"
[3], this will impact the Java target of the build.

See #8249 for context.

[1]: https://docs.gradle.org/current/javadoc/org/gradle/tooling/ConfigurableLauncher.html#setJavaHome(java.io.File)
[2]: https://docs.gradle.org/8.10/userguide/building_java_projects.html#sec:compiling_with_toolchain
[3]: https://docs.gradle.org/8.10/userguide/building_java_projects.html#sec:java_cross_compilation

Signed-off-by: Sebastian Schuberth <sebastian@doubleopen.org>

model/src/main/resources/reference.yml

@@ -104,6 +104,12 @@ ort:
         # another package manager generates files that this package manager requires to run correctly.
         mustRunAfter: [NPM]
 
+      GradleInspector:
+        options:
+          # An optional path to the Java home to use for Gradle project analysis. By default the Java version that ORT
+          # itself is run with will be used.
+          javaHome: "/path/to/java/home"
+
       Yarn2:
         options:
           # If set to true, disable verification of HTTPS certificate of remote registries. Useful when using a proxy to

model/src/test/kotlin/config/AnalyzerConfigurationTest.kt

@@ -136,9 +136,9 @@ class AnalyzerConfigurationTest : WordSpec({
         "override an existing entry" {
             val original = AnalyzerConfiguration(
                 packageManagers = mapOf(
-                    "Gradle" to PackageManagerConfiguration(
+                    "GradleInspector" to PackageManagerConfiguration(
                         mustRunAfter = listOf("Npm"),
-                        options = mapOf("gradleVersion" to "7.6.1")
+                        options = mapOf("gradleVersion" to "7.6.1", "javaHome" to "/path/to/java/home")
                     ),
                     "Npm" to PackageManagerConfiguration(
                         mustRunAfter = listOf("Yarn")
@@ -148,17 +148,17 @@ class AnalyzerConfigurationTest : WordSpec({
 
             val patched = AnalyzerConfiguration(
                 packageManagers = mapOf(
-                    "Gradle" to PackageManagerConfiguration(
+                    "GradleInspector" to PackageManagerConfiguration(
                         mustRunAfter = listOf("Npm"),
-                        options = mapOf("gradleVersion" to "8.0.2")
+                        options = mapOf("gradleVersion" to "8.0.2", "javaHome" to "/path/to/java/home")
                     ),
                     "Npm" to PackageManagerConfiguration(
                         mustRunAfter = listOf("Yarn")
                     )
                 )
             )
 
-            original.withPackageManagerOption("Gradle", "gradleVersion", "8.0.2") shouldBe patched
+            original.withPackageManagerOption("GradleInspector", "gradleVersion", "8.0.2") shouldBe patched
         }
 
         "add a non-existing entry" {

plugins/package-managers/gradle-inspector/src/main/kotlin/GradleInspector.kt

@@ -77,6 +77,11 @@ private val GRADLE_USER_HOME = Os.env["GRADLE_USER_HOME"]?.let { File(it) } ?: O
  */
 const val OPTION_GRADLE_VERSION = "gradleVersion"
 
+/**
+ * The name of the option to specify the Java home to use.
+ */
+const val OPTION_JAVA_HOME = "javaHome"
+
 /**
  * The [Gradle](https://gradle.org/) package manager for Java.
  *
@@ -160,6 +165,11 @@ class GradleInspector(
                     if (logger.delegate.isDebugEnabled && buildGradleVersion?.isEqualTo("8.5.0") != true) {
                         addProgressListener(ProgressListener { logger.debug(it.displayName) })
                     }
+
+                    options[OPTION_JAVA_HOME]?.also {
+                        logger.info { "Setting Java home for project analysis to '$it'." }
+                        setJavaHome(File(it))
+                    }
                 }
                 .setJvmArguments(jvmArgs)
                 .setStandardOutput(stdout)