Fix incorrect classpath leading to broken tests (#739)

The classpath on windows was pure fantasy and worked by fluke only if
java and all the code and dependencies where on the same drive.

if any code was on a different drive the classpath was mangled which
leads to tests failing.

e.g.  the classpath would end up being something like

D;\source\github\jenkins\remoting\target\test-classes;D;\source\github\jenkins\remoting\target\classes;C;\Users\jnord\.m2\repository\args4j\args4j\2.33\args4j-2.33.jar;C;\Users\jnord\.m2\repository\org\glassfish\tyrus\bundles\tyrus-standalone-client-jdk\2.1.5\tyrus-standalone-client-jdk-2.1.5.jar;C;\Users\jnord\.m2\repository\org\jenkins-ci\constant-pool-scanner\1.2\constant-pool-scanner-1.2.jar;C;\Users\jnord\.m2\repository\com\github\spotbugs\spotbugs-annotations\4.8.5\spotbugs-annotations-4.8.5.jar;C;\Users\jnord\.m2\repository\jakarta\websocket\jakarta.websocket-client-api\2.1.1\jakarta.websocket-client-api-2.1.1.jar;C;\Users\jnord\.m2\repository\net\jcip\jcip-annotations\1.0\jcip-annotations-1.0.jar;C;\Users\jnord\.m2\repository\org\kohsuke\access-modifier-annotation\1.33\access-modifier-annotation-1.33.jar;C;\Users\jnord\.m2\repository\org\jenkins-ci\annotation-indexer\1.17\annotation-indexer-1.17.jar;C;\Users\jnord\.m2\repository\com\google\guava\guava\31.0.1-jre\guava-31.0.1-jre.jar;C;\Users\jnord\.m2\repository\com\google\guava\failureaccess\1.0.1\failureaccess-1.0.1.jar;C;\Users\jnord\.m2\repository\com\google\guava\listenablefuture\9999.0-empty-to-avoid-conflict-with-guava\listenablefuture-9999.0-empty-to-avoid-conflict-with-guava.jar;C;\Users\jnord\.m2\repository\com\google\code\findbugs\jsr305\3.0.2\jsr305-3.0.2.jar;C;\Users\jnord\.m2\repository\org\checkerframework\checker-qual\3.12.0\checker-qual-3.12.0.jar;C;\Users\jnord\.m2\repository\com\google\errorprone\error_prone_annotations\2.7.1\error_prone_annotations-2.7.1.jar;C;\Users\jnord\.m2\repository\com\google\j2objc\j2objc-annotations\1.3\j2objc-annotations-1.3.jar;C;\Users\jnord\.m2\repository\commons-io\commons-io\2.16.1\commons-io-2.16.1.jar;C;\Users\jnord\.m2\repository\org\junit\jupiter\junit-jupiter\5.10.2\junit-jupiter-5.10.2.jar;C;\Users\jnord\.m2\repository\org\junit\jupiter\junit-jupiter-api\5.10.2\junit-jupiter-api-5.10.2.jar;C;\Users\jnord\.m2\repository\org\opentest4j\opentest4j\1.3.0\opentest4j-1.3.0.jar;C;\Users\jnord\.m2\repository\org\junit\platform\junit-platform-commons\1.10.2\junit-platform-commons-1.10.2.jar;C;\Users\jnord\.m2\repository\org\junit\jupiter\junit-jupiter-engine\5.10.2\junit-jupiter-engine-5.10.2.jar;C;\Users\jnord\.m2\repository\org\junit\jupiter\junit-jupiter-params\5.10.2\junit-jupiter-params-5.10.2.jar;C;\Users\jnord\.m2\repository\org\apiguardian\apiguardian-api\1.1.2\apiguardian-api-1.1.2.jar;C;\Users\jnord\.m2\repository\org\junit\vintage\junit-vintage-engine\5.10.2\junit-vintage-engine-5.10.2.jar;C;\Users\jnord\.m2\repository\org\junit\platform\junit-platform-engine\1.10.2\junit-platform-engine-1.10.2.jar;C;\Users\jnord\.m2\repository\junit\junit\4.13.2\junit-4.13.2.jar;C;\Users\jnord\.m2\repository\org\hamcrest\hamcrest-core\2.2\hamcrest-core-2.2.jar;C;\Users\jnord\.m2\repository\org\bouncycastle\bcpkix-jdk18on\1.78.1\bcpkix-jdk18on-1.78.1.jar;C;\Users\jnord\.m2\repository\org\bouncycastle\bcutil-jdk18on\1.78.1\bcutil-jdk18on-1.78.1.jar;C;\Users\jnord\.m2\repository\org\bouncycastle\bcprov-jdk18on\1.78.1\bcprov-jdk18on-1.78.1.jar;C;\Users\jnord\.m2\repository\org\hamcrest\hamcrest\2.2\hamcrest-2.2.jar;C;\Users\jnord\.m2\repository\org\jenkins-ci\test-annotations\1.4\test-annotations-1.4.jar;C;\Users\jnord\.m2\repository\org\mockito\mockito-core\5.11.0\mockito-core-5.11.0.jar;C;\Users\jnord\.m2\repository\net\bytebuddy\byte-buddy\1.14.12\byte-buddy-1.14.12.jar;C;\Users\jnord\.m2\repository\net\bytebuddy\byte-buddy-agent\1.14.12\byte-buddy-agent-1.14.12.jar;C;\Users\jnord\.m2\repository\org\objenesis\objenesis\3.3\objenesis-3.3.jar;C;\Users\jnord\.m2\repository\org\ow2\asm\asm\9.7\asm-9.7.jar;

which leads to
Error: Unable to initialize main class hudson.remoting.Launcher

This currently works in CI and elsewhere by pure fluke that the paths
without drives
(\Users\jnord\.m2\repository\org\hamcrest\hamcrest\2.2\hamcrest-2.2.jar)
use the current drive - which in CI will always be C: for java and the
source code and maven

amends #495

src/test/java/hudson/remoting/ForkRunner.java

@@ -61,13 +61,7 @@ public String getName() {
     }
 
     public String getClasspath() {
-        // this assumes we run in Maven
-        StringBuilder buf = new StringBuilder();
-        for (String entry : System.getProperty("java.class.path").split(":")) {
-            if (buf.length()>0) buf.append(File.pathSeparatorChar);
-            buf.append(entry);
-        }
-        return buf.toString();
+        return System.getProperty("java.class.path");
     }
 
     @Override