Tests broken on german machine because warning is given in german

[forki]

Our tests are not independent of the language settings of the developer machine.

Repro steps

Use german machine and run build.cmd all

Actual behaviour

Build is broken with the following changes:

[smoothdeveloper]

is there a way to flag them and set the thread culture arbitrarily?

[enricosada]

@smoothdeveloper yes with an internal use fsc argument LCID (used by ide), but that add a warning, so change a bit the diff of output.
i added #858 to add an additional --preferreduilang to fsc like roslyn to pass en-US, so tests can pass the language for case sensitive tests (i get same problem with italian)

problem is, the test can change culture, but we need to change culture of invoked fsc.exe (that's possibile only with an argument)

i think i need to rebase and ask for review

[forki]

Maybe we can disable the 4 tests for non-us systems? Or we remove the part that tests the culture specific message.

[enricosada]

the whole test is culture sensitive (diff the output of compiler) so cannot be fixed atm, but we can disable these ( nunit ignore ) on non en-US cultures. I'll send a pr, good idea @forki

[forki]

❤️ thanks for making this work.