Fix Gradle 9 toolchain probing for JavaExec tasks

Set explicit executable for runUnwindingValidator and unwindingReport
tasks to avoid Gradle 9 javaLauncher toolchain probing failures.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: jbachorik

build-logic/conventions/src/main/kotlin/com/datadoghq/profiler/ProfilerTestPlugin.kt

@@ -235,6 +235,9 @@ class ProfilerTestPlugin : Plugin<Project> {
                     runTask.mainClass.set(appMainClass)
                     runTask.classpath = sourceSets.getByName("main").runtimeClasspath + mainCfg
 
+                    // Use test JDK to avoid Gradle 9 toolchain probing issues
+                    runTask.setExecutable(PlatformUtils.testJavaExecutable())
+
                     if (testEnv.isNotEmpty()) {
                         testEnv.forEach { (key, value) ->
                             runTask.environment(key, value)
@@ -261,6 +264,9 @@ class ProfilerTestPlugin : Plugin<Project> {
                         "--output-file=build/reports/unwinding-summary.md"
                     )
 
+                    // Use test JDK to avoid Gradle 9 toolchain probing issues
+                    reportTask.setExecutable(PlatformUtils.testJavaExecutable())
+
                     if (testEnv.isNotEmpty()) {
                         testEnv.forEach { (key, value) ->
                             reportTask.environment(key, value)