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 gnome-3-32 in 7 minutes and 58 seconds (queued for 1 second)
Status Job ID Name Coverage
  Build
passed #290142
fedora-x86_64-autotools

00:04:39

passed #290141
fedora-x86_64-meson

00:01:07

passed #290144
win32
msys2-mingw32-autotools

00:07:29

passed #290143
win32
msys2-mingw32-meson

00:03:13

passed #290145
win32
vs2017-x64-meson

00:04:44