Add 'msvc_buildtools.ps1'

installation script for msvc 2019.

change the 16 to 15 for msvc 2017.

msvc_buildtools.ps1

@@ -0,0 +1,23 @@
+New-Item "temp" -ItemType "directory" -Force
+$client = New-Object System.Net.WebClient
+$client.DownloadFile("https://aka.ms/vs/16/release/channel", "temp\visualstudio.release.chman")
+$client.DownloadFile("https://aka.ms/vs/16/release/vs_buildtools.exe", "temp\vs_buildtools.exe")
+
+$args = @("--passive", "--wait", "--norestart",
+"--channelUri", ($pwd.path + "\temp\visualstudio.release.chman"),
+"--installChannelUri", ($pwd.path + "\temp\visualstudio.release.chman"),
+"--add", "Microsoft.VisualStudio.Workload.VCTools", "--includeRecommended",
+"--installPath", "C:\msvc")
+Start-Process "temp\vs_buildtools.exe" -ArgumentList $args -Wait
+
+$path = [System.Environment]::GetEnvironmentVariable("PATH", "User")
+$cmake = "C:\msvc\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin;"
+if(-not $path.Contains($cmake)){
+    [Environment]::SetEnvironmentVariable("PATH", $path + $cmake, "User")
+}
+
+$path = [System.Environment]::GetEnvironmentVariable("PATH", "User")
+$msbuild = "C:\msvc\MSBuild\Current\Bin;"
+if(-not $path.Contains($msbuild)){
+    [Environment]::SetEnvironmentVariable("PATH", $path + $msbuild, "User")
+}