Fix injecting argument to the command

[aboellinger]

Problem

Injection of the -P flag into the command to be run would only work if the args value was an empty string.

• exec_path="foo.exe" and args="" resulting into foo.exe -P bar.py was working
• exec_path="foo.exe" and args="baz" resulting into foo.exe baz-P bar.py was broken
  (expected result is foo.exe baz -P bar.py , note additionnal whitespace)

By the way, adding a blank space at the end of the arguments string in SG does not work because whitespaces get trimmed.

Solution

Simply add a whitespace before the -P argument (like with tk-harmony's -debug flag)

[aboellinger]

Note that this small patch is probably irrelevant if #9 is accepted.