Avoid a harmless error when Visual Studio is not installed

buildenvconf.md

@@ -14,19 +14,19 @@ System | [Dell Vostro 2521-9566 Q1 2013](http://www.dell.com/support/home/en/us/
 CPU | [Intel Core I3-2375M](https://ark.intel.com/products/74259/Intel-Core-i3-2375M-Processor-3M-Cache-1_50-GHz)
 RAM | 4GB DDR3 1600 MHz
 dGPU | None
-OS | Windows 10 October 2018 Update Pro x64
+OS | Windows 10 April 2019 Update Pro x64
 ### Visual Studio
 | | |
 |-|-|
 Edition | 2019 Community
-Version | 16.0.1
-Windows 10 SDK Version | 10.0.17763.132
-Windows 10 SDK install method | inbox via Visual Studio installer
+Version | 16.0.2
+Windows 10 SDK Version | 10.1.18362.1
+Windows 10 SDK install method | standalone
 ### LLVM
 | | |
 |-|-|
 LLVM Version | 8.0.0
-CMake version | 3.14.1
+CMake version | 3.14.3
 CMake ARCH | x64
 Ninja version | 1.9.0
 LLVM build configure x64[1] | cd llvm-8.0.0.src & md buildsys-x64-MT & cd buildsys-x64-MT & cmake -G "Ninja" -DLLVM_TARGETS_TO_BUILD=X86 -DCMAKE_BUILD_TYPE=Release -DLLVM_USE_CRT_RELEASE=MT -DLLVM_ENABLE_RTTI=1 -DLLVM_ENABLE_TERMINFO=OFF -DCMAKE_INSTALL_PREFIX=../x64-MT ..
@@ -41,7 +41,7 @@ pip version | 19.0.3
 setuptools version | 41.0.0
 pywin32 / pypiwin32 version | 224
 scons version | 3.0.5
-Mako version | 1.0.8
+Mako version | 1.0.9
 MarkupSafe version | 1.1.1
 wheel version | 0.33.1
 ### winflexbison

buildscript/modules/toolchain.cmd

@@ -5,18 +5,18 @@
 @IF /I %PROCESSOR_ARCHITECTURE%==x86 IF %abi%==x64 set vsabi=x86_x64
 @set vswhere="%ProgramFiles%
 @IF /I %PROCESSOR_ARCHITECTURE%==AMD64 set vswhere=%vswhere% (x86)
-@set vswhere=%vswhere%\Microsoft Visual Studio\Installer\vswhere.exe" -prerelease -property
+@set vswhere=%vswhere%\Microsoft Visual Studio\Installer\vswhere.exe"
 
 :findcompilers
 @set vsenv=%vswhere%
 @set totaltoolchains=0
 @set totalmsvc=0
-@for /F "USEBACKQ tokens=*" %%a IN (`%vswhere% catalog_productDisplayVersion`) do @set /a totalmsvc+=1&set /a totaltoolchains+=1
+@for /F "USEBACKQ tokens=*" %%a IN (`%vswhere% -prerelease -property catalog_productDisplayVersion`) do @set /a totalmsvc+=1&set /a totaltoolchains+=1
 @IF NOT %msysstate%==0 set /a totaltoolchains+=1
 @cls
 @setlocal ENABLEDELAYEDEXPANSION
 @set msvccount=0
-@for /F "USEBACKQ tokens=*" %%a IN (`%vswhere% catalog_productDisplayVersion`) do @set /a msvccount+=1&echo !msvccount!. Visual Studio %%a
+@IF EXIST %vswhere% for /F "USEBACKQ tokens=*" %%a IN (`%vswhere% -prerelease -property catalog_productDisplayVersion`) do @set /a msvccount+=1&echo !msvccount!. Visual Studio %%a
 @endlocal
 @IF NOT %msysstate%==0 echo %totaltoolchains%. MSYS2 Mingw-w64 GCC
 @echo.
@@ -50,9 +50,9 @@
 @rem Determine toolset version and build enviroment launcher PATH for selected Visual Studio installation
 @setlocal ENABLEDELAYEDEXPANSION
 @set msvccount=0
-@for /F "USEBACKQ tokens=*" %%a IN (`%vswhere% installationPath`) do @set /a msvccount+=1&IF !msvccount!==%selecttoolchain% set vsenv="%%a\VC\Auxiliary\Build\vcvarsall.bat"
+@for /F "USEBACKQ tokens=*" %%a IN (`%vswhere% -prerelease -property installationPath`) do @set /a msvccount+=1&IF !msvccount!==%selecttoolchain% set vsenv="%%a\VC\Auxiliary\Build\vcvarsall.bat"
 @set msvccount=0
-@for /F "USEBACKQ tokens=*" %%a IN (`%vswhere% catalog_productDisplayVersion`) do @set /a msvccount+=1&IF !msvccount!==%selecttoolchain% set toolset=%%a
+@for /F "USEBACKQ tokens=*" %%a IN (`%vswhere% -prerelease -property catalog_productDisplayVersion`) do @set /a msvccount+=1&IF !msvccount!==%selecttoolchain% set toolset=%%a
 @set toolset=%toolset:~0,2%
 @endlocal&set vsenv=%vsenv%&set toolset=%toolset%
 
@@ -62,7 +62,7 @@
 @IF NOT EXIST %vsenv% echo.
 @IF NOT EXIST %vsenv% IF /I NOT "%addvcpp%"=="y" pause
 @IF NOT EXIST %vsenv% IF /I NOT "%addvcpp%"=="y" GOTO findcompilers
-@IF NOT EXIST %vsenv% %vswhere:~0,-34%vs_installer.exe"
+@IF NOT EXIST %vsenv% %vswhere:~0,-12%vs_installer.exe"
 @IF NOT EXIST %vsenv% GOTO findcompilers
 
 :selectedcompiler