build,win: use latest installed VS by default

vcbuild.bat should detect what version of Visual Studio to use, it
should simply work without any parameter if any supported version is
installed. It should default to the latest version, to match the
behavior of `node-gyp`.

PR-URL: #13911
Fixes: #13641
Reviewed-By: Refael Ackermann <refack@gmail.com>

vcbuild.bat

@@ -15,7 +15,7 @@ if /i "%1"=="/?" goto help
 set config=Release
 set target=Build
 set target_arch=x64
-set target_env=vs2015
+set target_env=
 set noprojgen=
 set nobuild=
 set sign=
@@ -164,18 +164,18 @@ if %target_arch%==x64 if %msvs_host_arch%==amd64 set vcvarsall_arg=amd64
 
 @rem Look for Visual Studio 2017
 :vs-set-2017
-if "%target_env%" NEQ "vs2017" goto vs-set-2015
+if defined target_env if "%target_env%" NEQ "vs2017" goto vs-set-2015
 echo Looking for Visual Studio 2017
 @rem check if VS2017 is already setup, and for the requested arch
 if "_%VisualStudioVersion%_" == "_15.0_" if "_%VSCMD_ARG_TGT_ARCH%_"=="_%target_arch%_" goto found_vs2017
+@rem need to clear VSINSTALLDIR for vcvarsall to work as expected
 set "VSINSTALLDIR="
 call tools\msvs\vswhere_usability_wrapper.cmd
 if "_%VCINSTALLDIR%_" == "__" goto vs-set-2015
-@rem need to clear VSINSTALLDIR for vcvarsall to work as expected
 set vcvars_call="%VCINSTALLDIR%\Auxiliary\Build\vcvarsall.bat" %vcvarsall_arg%
 echo calling: %vcvars_call%
 call %vcvars_call%
-
+if errorlevel 1 goto vs-set-2015
 :found_vs2017
 echo Found MSVS version %VisualStudioVersion%
 set GYP_MSVS_VERSION=2017
@@ -184,11 +184,10 @@ goto msbuild-found
 
 @rem Look for Visual Studio 2015
 :vs-set-2015
-if "%target_env%" NEQ "vs2015" goto msbuild-not-found
+if defined target_env if "%target_env%" NEQ "vs2015" goto msbuild-not-found
 echo Looking for Visual Studio 2015
 if not defined VS140COMNTOOLS goto msbuild-not-found
 if not exist "%VS140COMNTOOLS%\..\..\vc\vcvarsall.bat" goto msbuild-not-found
-echo Found Visual Studio 2015
 if defined msi (
   echo Looking for WiX installation for Visual Studio 2015...
   if not exist "%WIX%\SDK\VS2015" (
@@ -201,6 +200,8 @@ if defined msi (
 call "%VS140COMNTOOLS%\..\..\vc\vcvarsall.bat"
 SET VCVARS_VER=140
 if not defined VCINSTALLDIR goto msbuild-not-found
+@rem Visual C++ Build Tools 2015 does not define VisualStudioVersion
+echo Found MSVS version 14.0
 set GYP_MSVS_VERSION=2015
 set PLATFORM_TOOLSET=v140
 goto msbuild-found