Add checks for libevent.so conflict with LSF

* LSF ships a `libevent.so` that is no related to the `libevent.so`
   shipped with Libevent.
 * Add some checks to the configure logic to detect scenarios where this
   conflict can be detected, and provide the user with a descriptive
   warning message.
   - When detected by `event/external` this is just a warning since
     the internal component may be able to be used instead.
     - This happens when the user supplies the LSF path via the
       `LDFLAGS` envar instead of via `--with-lsf-libdir`.
   - When detected by a LSF component and LSF was explicitly requested
     then this becomes an error. Otherwise it will just print the warning
     and that component will fail to build.
 * Note for `master` the `orter_check_lsf.m4` portion of this cherry-pick
   was moved to `prrte/config/prrte_check_lsf.m4`

Signed-off-by: Joshua Hursey <jhursey@us.ibm.com>
(cherry picked from commit fc4199e3ba)

opal/mca/event/external/configure.m4

@@ -116,10 +116,35 @@ AC_DEFUN([MCA_opal_event_external_CONFIG],[
                               [opal_event_external_support=yes],
                               [opal_event_external_support=no])
 
+           # Check to see if the above check failed because it conflicted with LSF's libevent.so
+           # This can happen if LSF's library is in the LDFLAGS envar or default search
+           # path. The 'event_fini' function is only defined in LSF's libevent.so and not
+           # in Libevent's libevent.so
+           AS_IF([test "$opal_event_external_support" = "no"],
+                 [AC_CHECK_LIB([event], [event_fini],
+                               [AC_MSG_WARN([===================================================================])
+                                AC_MSG_WARN([Possible conflicting libevent.so libraries detected on the system.])
+                                AC_MSG_WARN([])
+                                AC_MSG_WARN([LSF provides a libevent.so that is not from Libevent in its])
+                                AC_MSG_WARN([library path. It is possible that you have installed Libevent])
+                                AC_MSG_WARN([on the system, but the linker is picking up the wrong version.])
+                                AC_MSG_WARN([])
+                                AC_MSG_WARN([Configure may continue and attempt to use the 'internal' libevent])
+                                AC_MSG_WARN([instead of the 'external' libevent if you did not explicitly request])
+                                AC_MSG_WARN([the 'external' component.])
+                                AC_MSG_WARN([])
+                                AC_MSG_WARN([If your intention was to use the 'external' libevent then you need])
+                                AC_MSG_WARN([to address this linker path ordering issue. One way to do so is])
+                                AC_MSG_WARN([to make sure the libevent system library path occurs before the])
+                                AC_MSG_WARN([LSF library path.])
+                                AC_MSG_WARN([===================================================================])
+                                opal_event_external_support=no
+                               ])
+                 ])
+
            AS_IF([test "$opal_event_external_support" = "yes"],
                  [LDFLAGS="$opal_event_external_LDFLAGS $LDFLAGS"
-                  CPPFLAGS="$opal_event_external_CPPFLAGS $CPPFLAGS"],
-                 [])
+                  CPPFLAGS="$opal_event_external_CPPFLAGS $CPPFLAGS"])
 
            AS_IF([test "$opal_event_external_support" = "yes"],
                  [# Ensure that this libevent has the symbol