configure.ac: add warning when compiling on windows and MSVC lib not available

configure.ac

@@ -3432,3 +3432,12 @@ WARNING: hwloc was not enabled.  If the target machine is hyperthreaded the
 performance may be impacted a lot.  It is strongly recommended to install
 hwloc])
 fi
+
+if test x"$starpu_windows" = xyes -a "x$STARPU_MS_LIB" = "x"
+then
+  AC_MSG_NOTICE([
+WARNING: lib was not found, you will not be able to execute StarPU applications
+with Microsoft Visual Studio. Add to your PATH the directories for MSVC, e.g
+   c:\Program Files (x86)\Microsoft Visual Studio 11.0\Common7\IDE;
+   c:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin])
+fi