Add a simple FileSystemPath class that can canonicalize paths.

Also a simple StringBuilder to help him out.

AK/FileSystemPath.cpp

@@ -0,0 +1,44 @@
+#include "FileSystemPath.h"
+#include "Vector.h"
+#include "kstdio.h"
+#include "StringBuilder.h"
+
+namespace AK {
+
+FileSystemPath::FileSystemPath(const String& s)
+    : m_string(s)
+{
+    m_isValid = canonicalize();
+}
+
+bool FileSystemPath::canonicalize(bool resolveSymbolicLinks)
+{
+    // FIXME: Implement "resolveSymbolicLinks"
+    auto parts = m_string.split('/');
+    Vector<String> canonicalParts;
+
+    for (auto& part : parts) {
+        if (part == ".")
+            continue;
+        if (part == "..") {
+            if (!canonicalParts.isEmpty())
+                canonicalParts.takeLast();
+            continue;
+        }
+        canonicalParts.append(part);
+    }
+    if (canonicalParts.isEmpty()) {
+        m_string = "/";
+        return true;
+    }
+    StringBuilder builder;
+    for (auto& cpart : canonicalParts) {
+        builder.append('/');
+        builder.append(move(cpart));
+    }
+    m_string = builder.build();
+    return true;
+}
+
+}
+