use build script at root to simplify building everything

build.ps1

@@ -0,0 +1,14 @@
+Param(
+  [string]$build = "1.0.0-rc1-update1",
+  [string]$runtime = "clr",
+  [string]$architecture = "x64"
+)
+
+Write-Host "Setting DNVM version" -Foreground Green
+dnvm use $build -r $runtime -arch $architecture -p
+
+Write-Host "Building Rx.NET" -ForegroundColor Green
+.\Rx.NET\Source\build-new
+
+Write-Host "Building Ix.NET" -ForegroundColor Green
+.\Ix.NET\Source\build-new