build,win: set env before generating projects

vcbuild.bat calls python configure before setting GYP_MSVS_VERSION,
so SelectVisualStudioVersion (tools\gyp\pylib\gyp\MSVSVersion.py)
defaults to 'auto' and selects VS 2005.

vcbuild sets the environment in the current shell, so this issue
would manifest itself only on the first invocation of the script
in any given shell windows.

Reviewed-By: Julien Gilli <jgilli@fastmail.fm>
PR-URL: https://github.com/joyent/node/pull/20109

vcbuild.bat

@@ -102,24 +102,9 @@ if "%i18n_arg%"=="full-icu" set i18n_arg=--with-intl=full-icu
 if "%i18n_arg%"=="small-icu" set i18n_arg=--with-intl=small-icu
 if "%i18n_arg%"=="intl-none" set i18n_arg=--with-intl=none
 
-:project-gen
-@rem Skip project generation if requested.
-if defined noprojgen goto msbuild
-
 if defined NIGHTLY set TAG=nightly-%NIGHTLY%
 
-@rem Generate the VS project.
+@rem Set environment for msbuild
-SETLOCAL
-  if defined VS100COMNTOOLS call "%VS100COMNTOOLS%\VCVarsQueryRegistry.bat"
-  python configure %download_arg% %i18n_arg% %debug_arg% %nosnapshot_arg% %noetw_arg% %noperfctr_arg% --dest-cpu=%target_arch% --tag=%TAG%
-  if errorlevel 1 goto create-msvs-files-failed
-  if not exist node.sln goto create-msvs-files-failed
-  echo Project files generated.
-ENDLOCAL
-
-:msbuild
-@rem Skip project generation if requested.
-if defined nobuild goto sign
 
 @rem Look for Visual Studio 2013
 if not defined VS120COMNTOOLS goto vc-set-2012
@@ -152,13 +137,29 @@ if "%VCVARS_VER%" NEQ "100" (
   SET VCVARS_VER=100
 )
 if not defined VCINSTALLDIR goto msbuild-not-found
+set GYP_MSVS_VERSION=2010
 goto msbuild-found
 
 :msbuild-not-found
-echo Build skipped. To build, this file needs to run from VS cmd prompt.
+echo Failed to find Visual Studio installation.
-goto run
+goto exit
 
 :msbuild-found
+
+:project-gen
+@rem Skip project generation if requested.
+if defined noprojgen goto msbuild
+
+@rem Generate the VS project.
+python configure %download_arg% %i18n_arg% %debug_arg% %nosnapshot_arg% %noetw_arg% %noperfctr_arg% --dest-cpu=%target_arch% --tag=%TAG%
+if errorlevel 1 goto create-msvs-files-failed
+if not exist node.sln goto create-msvs-files-failed
+echo Project files generated.
+
+:msbuild
+@rem Skip project generation if requested.
+if defined nobuild goto sign
+
 @rem Build the sln with msbuild.
 msbuild node.sln /m /t:%target% /p:Configuration=%config% /clp:NoSummary;NoItemAndPropertyList;Verbosity=minimal /nologo
 if errorlevel 1 goto exit