[8.19] Platform-independent paths in TestBuildInfoPluginFuncTest (#128303) (#128376)

* Platform-independent paths in TestBuildInfoPluginFuncTest (#128303)

* Backport mysteriously missing part of 13a0e97

Author: prdoyle

build-tools/src/integTest/groovy/org/elasticsearch/gradle/test/TestBuildInfoPluginFuncTest.groovy

@@ -5,6 +5,8 @@ import com.fasterxml.jackson.databind.ObjectMapper
 import org.elasticsearch.gradle.fixtures.AbstractGradleFuncTest
 import org.gradle.testkit.runner.TaskOutcome
 
+import java.nio.file.Path
+
 class TestBuildInfoPluginFuncTest extends AbstractGradleFuncTest {
     def "basic functionality"() {
         given: