CI: update the LLVM-UWP image to a newer Clang/MingW version

This version uses msvcrt as the C runtime and not the UCRT which we can't
distribute on Win7 to Win8.1.
14 jobs for !18 with llvm-msvcrt in 19 minutes and 9 seconds (queued for 1 second)
latest detached
Status Job ID Name Coverage
  Build
canceled #400949
amd64 docker
android-arm

00:01:49

canceled #400950
amd64 docker
android-arm64

canceled #400951
amd64 docker
android-x86

canceled #400952
amd64 docker
android-x86_64

canceled #400943
amd64 docker
debian

00:01:47

canceled #400947
macos
ios-arm64

00:01:47

canceled #400948
macos
ios-armv7

00:01:45

canceled #400946
macos
macos

00:01:46

canceled #400945
amd64 docker
raspbian-arm

00:01:44

canceled #400944
amd64 docker
snap

00:01:44

canceled #400940
amd64 docker
win32

00:01:45

canceled #400941
amd64 docker
win64

00:01:44

passed #400953
docker amd64
win64-llvm

00:17:17

failed #400942
amd64 docker
win64-llvm

00:02:17