Build: Remove spawn from exec command (Windows)

[Chris--A]

It appears in ant that spawn on windows is not needed/usable with exec.

This error now is visible due to the commit here: 37e2a19, before hand it was ignored.

Currently a windows build generates this (using ant run):

windows-run:
spawn does not allow attributes related to input, output, error, result
spawn also does not allow timeout
finally, spawn is not compatible with a nested I/O

BUILD FAILED
F:\Arduino\build\build.xml:71: The following error occurred while executing this line:
F:\Arduino\build\build.xml:869: You have used an attribute or nested element which is not compatible with spawn

If I remove the spawn attribute everything compiles and runs fine.
If I remove the failonerror attribute, it also works fine.

It appears that spawn is only useful for background processes.

[ffissore]

Thanks! We need more windows hackers