In case others are struggling with CentOS 6.5 configure issues that I had, I'm providing the following unified diff patch
-Kip
#============================================== --- ../stunnel-5.08/configure.ac 2014-12-03 05:35:16.000000000 -0500 +++ ./configure.ac 2014-12-11 10:32:47.000000000 -0500 @@ -402,13 +402,13 @@ AC_MSG_RESULT([autodetecting]) # the library name has changed to -lsystemd in systemd 209 AC_SEARCH_LIBS([sd_listen_fds], [systemd systemd-daemon], - AC_CHECK_HEADERS([systemd/sd-daemon.h], [ + [ AC_CHECK_HEADERS([systemd/sd-daemon.h], [ AC_DEFINE([USE_SYSTEMD], [1], [Define to 1 to enable systemd socket activation]) AC_MSG_NOTICE([systemd support enabled]) ], [ AC_MSG_NOTICE([systemd header not found]) - ]), [ + ]) ], [ AC_MSG_NOTICE([systemd library not found]) ]) ] @@ -462,7 +462,8 @@ AC_MSG_CHECKING([for compiler sysroot]) if test "$GCC" = yes; then SYSROOT=`$CC --print-sysroot 2>/dev/null` -else +fi +if test -z "$SYSROOT" ; then SYSROOT="/" fi AC_MSG_RESULT([$SYSROOT])
#==============================================