meson: Specify encoding to UTF-8 when building with MSVC

Use build arguments consistent with core and -base. This can also
remove noisy "C4819" warning of non-us locale MSVC.
3 jobs for fix-c4819-warning in 6 minutes and 58 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Preparation
passed manifest #48838

00:00:21

 
  Build
passed build fedora x86_64 #48839

00:03:27

 
  Full Builds
passed build android arm64 api28 #48840

00:03:09