msi/tests: Fix compilation on systems that don't support nameless unions or structs.

[testbot at testbot.winehq.org]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
http://testbot.winehq.org/JobDetails.pl?Key=5078

Your paranoid android.


=== W7PROX64 (64 bit package) ===
package.c:8387: Test failed: Expected "C:\winetest\FileName1", got ""
package.c:8398: Test failed: Expected "C:\winetest\", got ""
package.c:8409: Test failed: Expected "C:\winetest\", got ""
package.c:8459: Test failed: Expected "C:\winetest\FileName3.dll", got ""
package.c:8470: Test failed: Expected "C:\winetest\FileName5.dll", got ""
package.c:8479: Test failed: Expected "C:\", got ""
package.c:8485: Test failed: Expected "C:\winetest\", got ""
package.c:8506: Test failed: Expected "C:\winetest\FileName1", got ""
package.c:8515: Test failed: Expected "C:\winetest\FileName1", got ""