use dotnet from host

build.ps1

@@ -1,24 +1,4 @@
 $repositoryRoot = split-path $MyInvocation.MyCommand.Definition
-$toolsPath = join-path $repositoryRoot ".dotnet"
-$getDotNet = join-path $toolsPath "dotnet-install.ps1"
-$nugetExePath = join-path $toolsPath "nuget.exe"
-
-write-host "Download latest install script from CLI repo"
-
-New-Item -type directory -f -path $toolsPath | Out-Null
-
-Invoke-WebRequest https://raw.githubusercontent.com/dotnet/cli/rel/1.0.0-preview2/scripts/obtain/dotnet-install.ps1 -OutFile $getDotNet
-
-$env:DOTNET_INSTALL_DIR="$repositoryRoot\.dotnet\win7-x64"
-
-if (!(Test-Path $env:DOTNET_INSTALL_DIR)) {
-    New-Item -type directory -path $env:DOTNET_INSTALL_DIR | Out-Null
-}
-
-
-& $getDotNet -arch x64
-
-$env:PATH = "$env:DOTNET_INSTALL_DIR;$env:PATH"
 
 Write-Host "Building Rx.NET" -ForegroundColor Green
 .\Rx.NET\Source\build-new