Windows Support: Testing Suite integration

Broaden support for execution of the test suite
on Windows.
General bug and review fixups

lib/spack/external/macholib/util.py

@@ -6,8 +6,6 @@
 
 from macholib import mach_o
 
-from llnl.util.symlink import symlink
-
 MAGIC = [
     struct.pack("!L", getattr(mach_o, "MH_" + _))
     for _ in ["MAGIC", "CIGAM", "MAGIC_64", "CIGAM_64"]
@@ -142,7 +140,7 @@ def mergetree(src, dst, condition=None, copyfn=mergecopy, srcbase=None):
         try:
             if os.path.islink(srcname):
                 realsrc = os.readlink(srcname)
-                symlink(realsrc, dstname)
+                os.symlink(realsrc, dstname)
             elif os.path.isdir(srcname):
                 mergetree(
                     srcname,