vuln-fix: Temporary Directory Hijacking or Information Disclosure (#389)

Simplify the creation of temp dir in FileMatchersTest

This was originally identified as a security vulnerability (see details below), but inspection of the code showed that the vulnerability was not actually present in the code, as the original code does check the return code of `directory.delete()` and `directory.mkdirs()`. The PR was accepted because the change actually is an improvement to the code anyway.

Weakness: CWE-379: Creation of Temporary File in Directory with Insecure Permissions
Severity: High
CVSSS: 7.3
Detection: CodeQL & OpenRewrite (https://public.moderne.io/recipes/org.openrewrite.java.security.UseFilesCreateTempDirectory)

Reported-by: Jonathan Leitschuh <Jonathan.Leitschuh@gmail.com>
Bug-tracker: JLLeitschuh/security-research#10
Co-authored-by: Moderne <team@moderne.io>

hamcrest/src/test/java/org/hamcrest/io/FileMatchersTest.java

@@ -5,6 +5,7 @@
 
 import java.io.File;
 import java.io.IOException;
+import java.nio.file.Files;
 
 import static org.hamcrest.core.IsEqual.equalTo;
 
@@ -16,9 +17,9 @@ public class FileMatchersTest extends AbstractMatcherTest {
 
     @Override
     protected void setUp() throws IOException {
-        directory = File.createTempFile("myDir", "");
-        assertTrue("deleting " + directory, directory.delete());
-        assertTrue("mkdir " + directory, directory.mkdirs());
+        directory = Files.createTempDirectory("myDir").toFile();
+        assertTrue("deleting " + directory, true);
+        assertTrue("mkdir " + directory, true);
 
         file = new File(directory, "myFile");
         file.createNewFile();