Forced include mechanism in FindComputeCpp.cmake does not work in Visual Studio 2015

[jpg85]

Forced include method doesn't work properly under VS2015.
The line:
set(forceIncludeFlags "/FI ${includedFile} /TP")
Gets split by spaces and the "includedFile" becomes part of the "AdditionalOptions" and a blank "ForcedIncludeFiles" tag is created.

If the line is changed to:
set(forceIncludeFlags "/FI${includedFile} /TP")
The ForcedInclude tag is properly populated with "includedFile". Note that I haven't tested the solution for paths with spaces or multiple files.

[MathiasMagnus]

Yes, apologies for that. The workaround code path for this issue was recently removed as a simplification to handling Visual Studio generators. It was I who introduced this workaround a long while ago and forgot what setup required it. Because VS 2017 does not need it anymore, I went ahead and removed it.

Seems like I'll have to put it back with a version check, and it should trigger only when using VS 2015.

[DuncanMcBain]

@MathiasMagnus we checked internally, it looks like the code change I made in #160 works on both '15 and '17 (having tested internally) so hopefully we don't even need a check + both syntaxes