bpo-30389 Adds detection of VS 2017 to distutils._msvccompiler (#1632)

diff --git a/PCbuild/build.bat b/PCbuild/build.bat
index 99d9ead..d4aebf5 100644
--- a/PCbuild/build.bat
+++ b/PCbuild/build.bat
@@ -84,7 +84,7 @@
 if "%~1"=="--no-ssl" (set IncludeSSL=false) & shift & goto CheckOpts
 if "%~1"=="--no-tkinter" (set IncludeTkinter=false) & shift & goto CheckOpts
 
-if "%IncludeExternals%"=="" set IncludeExternals=false
+if "%IncludeExternals%"=="" set IncludeExternals=true
 if "%IncludeSSL%"=="" set IncludeSSL=true
 if "%IncludeTkinter%"=="" set IncludeTkinter=true