build-sys: support old glibc versions without clock_gettime()

diff --git a/configure.ac b/configure.ac
index 76aa2a920ae2371295af8a67bbe3ff554d699bde..f71e15c456e7b5a3df486fb3acc81f748ee197b4 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -191,17 +191,22 @@ AM_CONDITIONAL([HAVE_PYTHON_DEVEL], [test "$have_python_devel" = "yes"])
 # ------------------------------------------------------------------------------
 
 AC_SEARCH_LIBS([dlsym], [dl], [], [AC_MSG_ERROR([*** Dynamic linking loader library not found])])
+AC_CHECK_HEADERS([sys/capability.h], [], [AC_MSG_ERROR([*** POSIX caps headers not found])])
+
+# unconditionally pull-in librt with old glibc versions
+AC_SEARCH_LIBS([clock_gettime], [rt], [], [])
 
 save_LIBS="$LIBS"
 LIBS=
 AC_SEARCH_LIBS([cap_init], [cap], [], [AC_MSG_ERROR([*** POSIX caps library not found])])
-AC_CHECK_HEADERS([sys/capability.h], [], [AC_MSG_ERROR([*** POSIX caps headers not found])])
 CAP_LIBS="$LIBS"
+AC_SUBST(CAP_LIBS)
+
+LIBS=
 AC_SEARCH_LIBS([mq_open], [rt], [], [AC_MSG_ERROR([*** POSIX RT library not found])])
 RT_LIBS="$LIBS"
 AC_SUBST(RT_LIBS)
 LIBS="$save_LIBS"
-AC_SUBST(CAP_LIBS)
 
 AC_CHECK_FUNCS([fanotify_init fanotify_mark])
 AC_CHECK_FUNCS([__secure_getenv secure_getenv])