xilinx_ise: do not attempt to source settings file on Windows

mibuild/xilinx_ise.py

@@ -1,4 +1,4 @@
-import os, struct, subprocess
+import os, struct, subprocess, sys
 from decimal import Decimal
 
 from migen.fhdl.structure import *
@@ -85,16 +85,19 @@ def _build_files(device, sources, named_sc, named_pc, build_name):
 -p %s""" % (build_name, build_name, device)
 	tools.write_to_file(build_name + ".xst", xst_contents)
 
+def _is_valid_version(path, v):
+	try: 
+		Decimal(v)
+		return os.path.isdir(os.path.join(path, v))
+	except:
+		return False
+
 def _run_ise(build_name, ise_path, source):
-	def is_valid_version(v):
-		try: 
-			Decimal(v)
-			return os.path.isdir(os.path.join(ise_path, v))
-		except:
-			return False
+	if sys.platform == "win32" or sys.platform == "cygwin":
+		source = False
 	build_script_contents = "# Autogenerated by mibuild\nset -e\n"
 	if source:
-		vers = [ver for ver in os.listdir(ise_path) if is_valid_version(ver)]
+		vers = [ver for ver in os.listdir(ise_path) if _is_valid_version(ise_path, ver)]
 		tools_version = max(vers)
 		bits = struct.calcsize("P")*8
 		xilinx_settings_file = '%s/%s/ISE_DS/settings%d.sh' % (ise_path, tools_version, bits)