Automatically initialize x64 environment if CL.exe is missing + make sure found CL.exe is for x64 (credit to mmozeiko)

build.bat

@@ -2,6 +2,21 @@
 
 setlocal EnableDelayedExpansion
 
+where /Q cl.exe || (
+  set __VSCMD_ARG_NO_LOGO=1
+  for /f "tokens=*" %%i in ('"C:\Program Files (x86)\Microsoft Visual Studio\Installer\vswhere.exe" -latest -requires Microsoft.VisualStudio.Workload.NativeDesktop -property installationPath') do set VS=%%i
+  if "!VS!" equ "" (
+    echo ERROR: Visual Studio installation not found
+    exit /b 1
+  )  
+  call "!VS!\VC\Auxiliary\Build\vcvarsall.bat" amd64 || exit /b 1
+)
+
+if "%VSCMD_ARG_TGT_ARCH%" neq "x64" (
+  echo ERROR: please run this from MSVC x64 native tools command prompt, 32-bit target is not supported!
+  exit /b 1
+)
+
 for /f "usebackq tokens=1,2 delims=,=- " %%i in (`wmic os get LocalDateTime /value`) do @if %%i==LocalDateTime (
 	set CURR_DATE_TIME=%%j
 )