Revamp classpath search to use normalized paths

On Windows with Java 11, the `java.class.path` property contains
backslash-escaped backslashes, as in "`C:\\foo\\bar`".  These doubled
backslashes interfere with the logic for finding classpath entries that
contain the requested element.  Using normalized paths for all
comparisons seems to fix the problem, and will likely be more robust in
general.

Author: liblit

com.ibm.wala.core/src/testFixtures/java/com/ibm/wala/core/tests/util/WalaTestCase.java

@@ -16,6 +16,9 @@
 import com.ibm.wala.ssa.SSAOptions;
 import com.ibm.wala.util.heapTrace.HeapTracer;
 import java.io.File;
+import java.nio.file.Paths;
+import java.util.Arrays;
+import java.util.stream.Collectors;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.runner.JUnitCore;
@@ -63,22 +66,20 @@ protected static void justThisTest(Class<?> testClass) {
   }
 
   protected static String getClasspathEntry(String elt) {
-    StringBuilder result = null;
-    for (String s : System.getProperty("java.class.path").split(File.pathSeparator)) {
-      if (s.contains(elt)) {
-        File e = new File(s);
-        assert e.exists() : elt + " expected to exist";
-        if (e.isDirectory() && !s.endsWith("/")) {
-          s += '/';
-        }
-        if (result == null) {
-          result = new StringBuilder(s);
-        } else {
-          result.append(File.pathSeparator).append(s);
-        }
-      }
-    }
-    assert result != null : "cannot find " + elt;
-    return result.toString();
+    final String normalizedElt = Paths.get(elt).normalize().toString();
+    final String result =
+        Arrays.stream(System.getProperty("java.class.path").split(File.pathSeparator))
+            .map(candidate -> Paths.get(candidate).normalize())
+            .filter(candidate -> candidate.toString().contains(normalizedElt))
+            .map(
+                found -> {
+                  final String foundString = found.toString();
+                  return found.toFile().isDirectory()
+                      ? foundString + File.separatorChar
+                      : foundString;
+                })
+            .collect(Collectors.joining(File.pathSeparator));
+    assert !result.isEmpty() : "cannot find " + elt;
+    return result;
   }
 }