tools/msvc/starpu_exec.bat: fix directory for MVSC (should do it through a environment variable)

tools/msvc/starpu_exec.bat

@@ -2,7 +2,7 @@
 
 REM StarPU --- Runtime system for heterogeneous multicore architectures.
 REM
-REM Copyright (C) 2013, 2014, 2015  CNRS
+REM Copyright (C) 2013, 2014, 2015, 2017  CNRS
 REM
 REM StarPU is free software; you can redistribute it and/or modify
 REM it under the terms of the GNU Lesser General Public License as published by
@@ -29,7 +29,7 @@ FOR %%F IN (%STARPU_PATH%\bin\*dll) DO COPY %%F starpu\%%~nF
 FOR %%F IN (%HWLOC%\bin\*dll) DO COPY %%F starpu
 
 set STARPU_OLDPATH=%PATH%
-call "C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat" x86
+call "C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\vcvarsall.bat" x86
 cl %1 %STARPU_CFLAGS% %STARPU_LDFLAGS%
 
 set PATH=starpu;c:\MinGW\bin;%PATH%