Breaking change in msbuild.sh

[sbomer]

After https://github.com/dotnet/arcade/pull/1423/files, msbuild.sh no longer sets NUGET_PACKAGES, causing the following error when using it to build an arcade project:

018-12-13T20:13:54.4060639Z ./eng/common/msbuild.sh --ci src/publishwitharcade.proj /p:__BuildType=Release /p:__BuildArch=arm
2018-12-13T20:13:54.4102191Z [command]/bin/bash --noprofile --norc /__w/_temp/1bc9b032-b9a9-4f00-967f-0b83a3b0254f.sh
2018-12-13T20:13:56.0898580Z /__w/7/s/src/publishwitharcade.proj(8,3): error : Unable to find package Microsoft.DotNet.Arcade.Sdk. No packages exist with this id in source(s): myget.org dotnet-core, nuget.org
2018-12-13T20:13:56.0935604Z /__w/7/s/src/publishwitharcade.proj(8,31): error MSB4236: The SDK 'Microsoft.DotNet.Arcade.Sdk' specified could not be found.
2018-12-13T20:13:56.1013752Z 
2018-12-13T20:13:56.1025489Z Build FAILED.
2018-12-13T20:13:56.1025627Z 

[JohnTortugo]

@sbomer is this a blocking issue for your team?

Cc @tmat

[sbomer]

@JohnTortugo No, I worked around it by setting NUGET_PACKAGES from outside msbuild.sh. Thanks for checking!

[tmat]

msbuild.ps1/sh needs to call GetNuGetPackageCachePath now before calling MSBuild function.

[jcagme]

@sbomer did things work after what @tmat pointed out?

[sbomer]

@jcagme If I understand correctly, @tmat's suggestion is what needs to be done on the arcade side to fix msbuild.sh/ps1.

[jcagme]

Oh yeah, I misread what @tmat propoced as passing a new property to the script :)