Add nasm to Win containers (#1884)

This is a build dependency of optimized assembler code for software
decoders.

b/281831576

docker/windows/base/build/Dockerfile

@@ -34,6 +34,8 @@ RUN iex ((New-Object System.Net.WebClient).DownloadString('https://chocolatey.or
     choco install -y -c C:\choco-cache nodejs-lts;`
     choco install -y -c C:\choco-cache git;`
     choco install -y -c C:\choco-cache cmake --installargs 'ADD_CMAKE_TO_PATH=System';`
+    choco install -y -c C:\choco-cache nasm;`
+    setx /M PATH $($Env:PATH + ';C:\Program Files\NASM');`
     Write-Host ('Deleting the chocolately download cache');`
     Remove-Item -Force -Recurse $env:TEMP\*;`
     C:\fast-win-rmdir.cmd C:\choco-cache;`