build: Force-include msvc_recommended_pragmas.h on Visual Studio

By doing so, we essentially cover the various compiler flags that we
want to use for non-Visual Studio builds to check for warnings that
might cause real concern.

This also skips the checks for the various GCC-isque CFlag checks that
are scattered in the various build files on Visual Studio builds, since
they are essentially meaningless on Visual Studio builds.
5 jobs for <span class="ref-name">msvc-pragmas-stable</span> in 11 minutes and 6 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #290115
fedora-x86_64-autotools

00:02:43

passed #290114
fedora-x86_64-meson

00:01:07

passed #290117
win32
msys2-mingw32-autotools

00:07:53

passed #290116
win32
msys2-mingw32-meson

00:03:09

passed #290118
win32
vs2017-x64-meson

00:04:51