compiler: work around idiotic windoze behavior that causes conda ld.lld not to be found

artiq/compiler/targets.py

@@ -28,8 +28,10 @@ class RunTool:
         for argument in self._pattern:
             cmdline.append(argument.format(**self._tempnames))
 
+        # https://bugs.python.org/issue17023
+        windows = os.name == "nt"
         process = subprocess.Popen(cmdline, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
-                                   universal_newlines=True)
+                                   universal_newlines=True, shell=windows)
         stdout, stderr = process.communicate()
         if process.returncode != 0:
             raise Exception("{} invocation failed: {}".