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 5 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Preparation
passed manifest #48855

00:00:25

 
  Build
passed build fedora x86_64 #48856

00:02:55

 
  Full Builds
passed build android arm64 api28 #48857

00:02:44