From: Abbas Naderi <abiusx@chromium.org>
CL-URL: https://chromium-review.googlesource.com/c/501988
Project-Bug-URL: https://bugs.chromium.org/p/chromium/issues/detail?id=720151

Fixes libevent lookup.

nfs-utils build relies on libevent for NFSv4 support.
However, libevent is hardcoded as -levent, whereas
recent versions expose -levent_core.

The patch uses pkg-config to lookup the library and
replaces the previous LIBEVENT variable with it,
because the lib is not always used.


--- aclocal/libevent.m4
+++ aclocal/libevent.m4
@@ -2,9 +2,13 @@ dnl Checks for libevent
 AC_DEFUN([AC_LIBEVENT], [
 
   dnl Check for libevent, but do not add -levent to LIBS
-  AC_CHECK_LIB([event], [event_dispatch], [LIBEVENT=-levent],
-               [AC_MSG_ERROR([libevent not found.])])
-  AC_SUBST(LIBEVENT)
+  dnl LIBEVENT is the variable used, but PKG_CHECK_MODULES
+  dnl 	exposes V_LIBS and V_CFLAGS, so set LIBEVENT var
+  dnl 	to the result of pkg-config check. This approach
+  dnl 	prevents libevent libs to be added to LIBS.
+  PKG_CHECK_MODULES([LIBEVENT], [libevent])
+  AC_SUBST(LIBEVENT, $LIBEVENT_LIBS)
+  CPPFLAGS="$CPPFLAGS $LIBEVENT_CFLAGS"
 
   AC_CHECK_HEADERS([event.h], ,
                    [AC_MSG_ERROR([libevent headers not found.])])