buildNormalizedPath

assert(DirPath("/etc").buildNormalizedPath(FileName("foo")) == FilePath("/etc/foo"));
assert(DirPath("/etc").buildNormalizedPath(FilePath("foo")) == FilePath("/etc/foo"));
assert(DirPath("/usr").buildNormalizedPath(DirName("bin")) == DirPath("/usr/bin"));
assert(DirPath("/usr").buildNormalizedPath(DirPath("bin")) == DirPath("/usr/bin"));
assert(DirPath("/usr").buildNormalizedPath(DirPath("/bin")) == DirPath("/bin"));