Two little errors in manual_cpp

- execvp needs the programs name also as first argument in the argument
  list
- len(files) == 1 (i.e. the normal case) was omitted in the last second
  when the error handling was improved

manual_cpp

@@ -19,8 +19,11 @@ def check_call_redirect(args, filename=None, **kwargs):
     if os.getenv("V") == "1":
         print(" ".join(args), ">", filename)
     with open(filename, "wb") as fd:
-        return subprocess.check_call(args, stdout=fd, **kwargs)
-
+        try:
+            return subprocess.check_call(args, stdout=fd, **kwargs)
+        except subprocess.CalledProcessError as e:
+            os.remove(filename)
+            raise SystemExit(e.returncode)
 
 args = sys.argv[1:]
 cpp_args = filter(cpp_arg, args)
@@ -31,7 +34,9 @@ if len(files) > 1:
     raise Exception("Specify exactly one .F90 file")
 elif len(files) == 0:
     # No .F90 file specified, execute program as-is
-    os.execvp(args[0], args[1:])
+    os.execvp(args[0], args[0:])
+elif len(files) == 1:
+    file, = files
 
 tmp_filename = "manually_preprocessed_" + file.replace("/", "__")