win: backport set env before generating projects

Backport commit a58b174 from branch
v0.12.

Original commit message:

  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: #20109

Conflicts:
	vcbuild.bat

vcbuild.bat

@@ -81,25 +81,6 @@ if defined nosnapshot set nosnapshot_arg=--without-snapshot
 if defined noetw set noetw_arg=--without-etw& set noetw_msi_arg=/p:NoETW=1
 if defined noperfctr set noperfctr_arg=--without-perfctr& set noperfctr_msi_arg=/p:NoPerfCtr=1
 
-: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.
-SETLOCAL
-  if defined VS100COMNTOOLS call "%VS100COMNTOOLS%\VCVarsQueryRegistry.bat"
-  python configure %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
 if not exist "%VS120COMNTOOLS%\..\..\vc\vcvarsall.bat" goto vc-set-2012
@@ -122,13 +103,31 @@ if not defined VS100COMNTOOLS goto msbuild-not-found
 if not exist "%VS100COMNTOOLS%\..\..\vc\vcvarsall.bat" goto msbuild-not-found
 call "%VS100COMNTOOLS%\..\..\vc\vcvarsall.bat"
 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.
-goto run
+echo Failed to find Visual Studio installation.
+goto exit
 
 :msbuild-found
+
+: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.
+python configure %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