bug: Build::is_flag_supported /guard:cf returns false on 1.2.4 ->1.2.5 transition (on x86_64-pc-windows-msvc)

[omerkattan-microsoft]

Seems related to #1324
The build output looks like that in 1.2.5, while these messages don't show up in 1.2.4:

When manually running the flag check command I get the following output:

This in practice disables control flow guard mitigation for projects compiled with cc.
It is possible that /guard:cf adds a link dependency on MSVCRT.lib and the fix for #1324 didn't take that into account.

[ChrisDenton]

Oh, that's not great. Fix in #1417.

[omerkattan-microsoft]

Wow that was quick!
I confirmed that the issue does not reproduce on your branch.
Thank you!