schannel: disable client cert path feature if APIs not available

[ArchangelSDY]

Original MinGW targets Windows 2000 by default, which lacks some APIs and definitions for this feature. Disable it if required APIs not available.

@mback2k Could you help review that if the __MINGW_H macro is sufficient for the judgement? I know little about MinGW.

[mback2k]

Please do not disable this feature for all MinGW builds. MinGW-w64 and Msys2 provide updated APIs which include the required definitions, see the other builds here: https://curlbuild.uxnr.de/waterfall (only 2 of them are failing.)

Please check for the required API instead. Another approach would be to add the required definitions if they are missing, like here: https://github.com/curl/curl/blob/master/lib/vtls/schannel.c#L99

[ArchangelSDY]

OK. Updated to check macro definitions.

[bagder]

@mback2k looking like a 👍 for you too?

[jay]

what about convert the hex to binary on our own

[ArchangelSDY]

Well, basically I don't think it's a good idea to re-invent a function in a crypto library. Since MinGW seems not to be actively maintained, MinGW-w64 should be a better choice.

[jay]

Thanks

[mback2k]

Sorry for my absence. Thanks a lot.

[bagder]

I had to polish the schannel code slightly with f0c466d, but it shouldn't cause any problems...