Update dependencies from https://github.com/dotnet/arcade build 20190117.6 (#306)

This change updates the following dependencies
- Microsoft.DotNet.Arcade.Sdk - 1.0.0-beta.19067.6

eng/common/sdk-task.ps1

@@ -0,0 +1,74 @@
+[CmdletBinding(PositionalBinding=$false)]
+Param(
+  [string] $projects = "",
+  [string][Alias('v')]$verbosity = "minimal",
+  [string] $msbuildEngine = $null,
+  [bool] $warnAsError = $true,
+  [switch][Alias('bl')]$binaryLog,
+  [switch][Alias('r')]$restore,
+  [switch] $ci,
+  [switch] $prepareMachine,
+  [switch] $help,
+  [Parameter(ValueFromRemainingArguments=$true)][String[]]$properties
+)
+
+. $PSScriptRoot\tools.ps1
+
+function Print-Usage() {
+    Write-Host "Common settings:"
+    Write-Host "  -v[erbosity] <value>    Msbuild verbosity: q[uiet], m[inimal], n[ormal], d[etailed], and diag[nostic]"
+    Write-Host "  -[bl|binaryLog]         Output binary log (short: -bl)"
+    Write-Host "  -help                   Print help and exit"
+    Write-Host ""
+
+    Write-Host "Advanced settings:"
+    Write-Host "  -restore                Restore dependencies (short: -r)"
+    Write-Host "  -projects <value>       Semi-colon delimited list of sln/proj's from the Arcade sdk to build. Globbing is supported (*.sln)"
+    Write-Host "  -ci                     Set when running on CI server"
+    Write-Host "  -prepareMachine         Prepare machine for CI run"
+    Write-Host "  -msbuildEngine <value>  Msbuild engine to use to run build ('dotnet', 'vs', or unspecified)."
+    Write-Host ""
+    Write-Host "Command line arguments not listed above are passed thru to msbuild."
+    Write-Host "The above arguments can be shortened as much as to be unambiguous (e.g. -co for configuration, -t for test, etc.)."
+}
+
+function Build {
+  $toolsetBuildProj = InitializeToolset
+
+  $toolsetBuildProj = Join-Path (Split-Path $toolsetBuildProj -Parent) "SdkTasks\SdkTask.proj"
+  $bl = if ($binaryLog) { "/bl:" + (Join-Path $LogDir "SdkTask.binlog") } else { "" }
+  MSBuild $toolsetBuildProj `
+    $bl `
+    /p:Projects=$projects `
+    /p:Restore=$restore `
+    /p:RepoRoot=$RepoRoot `
+    /p:ContinuousIntegrationBuild=$ci `
+    @properties
+}
+
+try {
+  if ($help -or (($null -ne $properties) -and ($properties.Contains("/help") -or $properties.Contains("/?")))) {
+    Print-Usage
+    exit 0
+  }
+
+  if ($projects -eq "") {
+    Write-Error "Missing required parameter '-projects <value>'"
+    Print-Usage
+    ExitWithExitCode 1
+  }
+
+  if ($ci) {
+    $binaryLog = $true
+  }
+
+  Build
+}
+catch {
+  Write-Host $_
+  Write-Host $_.Exception
+  Write-Host $_.ScriptStackTrace
+  ExitWithExitCode 1
+}
+
+ExitWithExitCode 0