Support VS 2017/19

Author: Jand42

build.cmd

@@ -12,7 +12,12 @@ if not "%BuildBranch%"=="" (
 )
 
 if "%VisualStudioVersion%"=="" (
-  set VisualStudioVersion=15.0
+  if exist "%ProgramFiles(x86)%\Microsoft Visual Studio\2017\" (
+    set VisualStudioVersion=15.0
+  )
+  if exist "%ProgramFiles(x86)%\Microsoft Visual Studio\2019\" (
+    set VisualStudioVersion=16.0
+  )
 )
 
 :: Allow running `build SomeTask` instead of `build -t SomeTask`
@@ -23,4 +28,4 @@ if "%_Add-t%"=="1" (
   .paket\fake.exe run build.fsx -t %*
 ) else (
   .paket\fake.exe run build.fsx %*
-)
+)