fix dynare++ build on OS X

(cherry picked from commit e3762580)

configure.ac

@@ -153,12 +153,17 @@ AM_CONDITIONAL([HAVE_CWEAVE], [test "x$CWEAVE" != "x"])
 
 AC_PROG_F77
 AC_F77_LIBRARY_LDFLAGS
-# Hack to get static linking of libgfortran on MinGW
-# (-static-libgfortran doesn't act on gcc/g++)
 case ${host_os} in
   *mingw32*)
+    # Hack to get static linking of libgfortran on MinGW
+    # (-static-libgfortran doesn't act on gcc/g++)
     FLIBS=`echo $FLIBS | sed 's/-lgfortran/-Wl,-Bstatic -lgfortran -Wl,-Bdynamic/'`
     ;;
+  *darwin*)
+    # * OS X doesn't need to link against the Fortran libraries because
+    #   everything is contained within the vecLib framework.
+    FLIBS=''
+    ;;
 esac
 
 if test "x$F77" != "x"; then