Use absolute path for temporary directory in tests (#52228)

We explicitly set the path for the temporary directory to use in test
tasks, but today this path is a relative path, relative to the current
working directory of the test task. The fact that we are using a
relative path here appears to be legacy, simply leftover from the days
of the Maven build. An absolute path is preferred here, since it's
explicit and we do not have to rely on everyone resolving the path
properly relative to the working directory.

Author: jasontedor

buildSrc/src/main/groovy/org/elasticsearch/gradle/BuildPlugin.groovy

@@ -732,17 +732,14 @@ class BuildPlugin implements Plugin<Project> {
                     test.jvmArgs '-ea', '-esa'
                 }
 
-                // we use './temp' since this is per JVM and tests are forbidden from writing to CWD
                 test.systemProperties 'gradle.dist.lib': new File(project.class.location.toURI()).parent,
-                        'java.io.tmpdir': './temp',
                         'java.awt.headless': 'true',
                         'tests.gradle': 'true',
                         'tests.artifact': project.name,
                         'tests.task': test.path,
                         'tests.security.manager': 'true',
                         'jna.nosys': 'true'
 
-
                 // ignore changing test seed when build is passed -Dignore.tests.seed for cacheability experimentation
                 if (System.getProperty('ignore.tests.seed') != null) {
                     nonInputProperties.systemProperty('tests.seed', BuildParams.testSeed)
@@ -753,6 +750,8 @@ class BuildPlugin implements Plugin<Project> {
                 // don't track these as inputs since they contain absolute paths and break cache relocatability
                 nonInputProperties.systemProperty('gradle.worker.jar', "${project.gradle.getGradleUserHomeDir()}/caches/${project.gradle.gradleVersion}/workerMain/gradle-worker.jar")
                 nonInputProperties.systemProperty('gradle.user.home', project.gradle.getGradleUserHomeDir())
+                // we use 'temp' relative to CWD since this is per JVM and tests are forbidden from writing to CWD
+                nonInputProperties.systemProperty('java.io.tmpdir', test.workingDir.toPath().resolve('temp'))
 
                 nonInputProperties.systemProperty('compiler.java', "${-> BuildParams.compilerJavaVersion.majorVersion}")