setup: always create a support dir and populate it with a site-packages and add same to the PYTHONPATH, just in case someone is going to do "build", "develop", or "test" or something else which triggers a build

I think there must be a much better solution for this -- probably to fix setuptools #54 and ship our own fork of setuptools and rely on it.

setup.py

@@ -22,17 +22,28 @@ def pylibdir(prefixdir):
 basedir = os.path.dirname(os.path.abspath(__file__))
 supportlib = pylibdir(os.path.join(basedir, "support"))
 
-
+prefixdirs = [] # argh!  horrible kludge to work-around setuptools #54
 for i in range(len(sys.argv)):
     arg = sys.argv[i]
-    prefixdir = None
     if arg.startswith("--prefix="):
-        prefixdir = arg[len("--prefix="):]
+        prefixdirs.append(arg[len("--prefix="):])
     if arg == "--prefix":
         if len(sys.argv) > i+1:
-            prefixdir = sys.argv[i+1]
+            prefixdirs.append(sys.argv[i+1])
 
-    if prefixdir:
+    if arg.startswith("develop") or arg.startswith("build") or arg.startswith("test"): # argh! horrible kludge to workaround setuptools #17
+        if sys.platform == "linux2":
+            # workaround for tahoe #229 / setuptools #17, on debian
+            sys.argv.extend(["--site-dirs", "/var/lib/python-support/python%d.%d" % (sys.version_info[:2])])
+        elif sys.platform == "darwin":
+            # this probably only applies to leopard 10.5, possibly only 10.5.5
+            sd = "/System/Library/Frameworks/Python.framework/Versions/%d.%d/Extras/lib/python" % (sys.version_info[:2])
+            sys.argv.extend(["--site-dirs", sd])
+
+if not prefixdirs:
+    prefixdirs.append("support")
+
+for prefixdir in prefixdirs:
     libdir = pylibdir(prefixdir)
     try:
         os.makedirs(libdir)
@@ -44,15 +55,6 @@ for i in range(len(sys.argv)):
     pp.append(libdir)
     os.environ['PYTHONPATH'] = os.pathsep.join(pp)
 
-    if arg.startswith("develop") or arg.startswith("build") or arg.startswith("test"): # argh! horrible kludge to workaround setuptools #17
-        if sys.platform == "linux2":
-            # workaround for tahoe #229 / setuptools #17, on debian
-            sys.argv.extend(["--site-dirs", "/var/lib/python-support/python%d.%d" % (sys.version_info[:2])])
-        elif sys.platform == "darwin":
-            # this probably only applies to leopard 10.5, possibly only 10.5.5
-            sd = "/System/Library/Frameworks/Python.framework/Versions/%d.%d/Extras/lib/python" % (sys.version_info[:2])
-            sys.argv.extend(["--site-dirs", sd])
-
 try:
     from ez_setup import use_setuptools
 except ImportError: