userspace: Implement pwd utility

userspace/programs/pwd/main.cpp

@@ -0,0 +1,15 @@
+#include <limits.h>
+#include <stdio.h>
+#include <unistd.h>
+
+int main()
+{
+	char buffer[PATH_MAX];
+	if (getcwd(buffer, PATH_MAX) == nullptr)
+	{
+		perror("getcwd");
+		return 1;
+	}
+
+	printf("%s\n", buffer);
+}