Make appveyor build both release and debug

[Bigbossbro08]

I tried to compile the project with Visual Studio. It seems Visual Studio is failing to compile such big line. Tried to small string by different lines but no real luck.

Log output:
grammar.gen.tab.hpp(2833): error C2026: string too big, trailing characters truncated [F:\freeaoe\build\freeaoe_common.vcxproj

[Bigbossbro08]

Seems like I fixed it by changing debug to release. It helps but removes all those independence for debugging on Windows Visual Studio.

[sandsmark]

hmm, unfortunately that one is automatically generated. and VS is the only automatic CI system set up, but I should probably set it to build both in release and debug.

[SmallJoker]

I don't think 2017 is now enough to build freeaoe. 1744a69 increased the required C++ version to 20.

freeaoe/CMakeLists.txt

Line 8 in 97b4435

set (CMAKE_CXX_STANDARD 20)