Fix bug with locate and python detection in m4/ax_python.m4

m4/ax_python.m4

@@ -64,7 +64,7 @@ ax_python_bin=$PYTHON_BIN
 if test x$ax_python_bin != x; then
    AC_CHECK_LIB($ax_python_bin, main, ax_python_lib=$ax_python_bin, ax_python_lib=no)
    AC_CHECK_HEADER([$ax_python_bin/Python.h],
-   [[ax_python_header=`locate -n 1 $ax_python_bin/Python.h | sed -e s,/Python.h,,`]],
+   [[ax_python_header=`locate $ax_python_bin/Python.h | head -n 1 | sed -e s,/Python.h,,`]],
    ax_python_header=no)
    if test "$ax_python_lib" != "no"; then
      if test "$ax_python_header" != "no"; then