Solaris provides backtrace via libc directly, so use AC_SEARCH_LIBS instead
for a simpler way of finding this function.
Need to file upstream bug; appropriate as-is
--- gnome-session-3.16.0/configure.ac 2015-03-23 10:27:18.000000000 -0700
+++ gnome-session-3.16.0/configure.ac 2015-07-06 22:30:31.155697361 -0700
@@ -296,12 +296,7 @@
dnl ====================================================================
AC_CHECK_HEADERS(execinfo.h)
-AC_CHECK_LIB(execinfo, backtrace, [have_backtrace="yes"], [have_backtrace="no"])
-EXECINFO_LIBS=""
-if test "x$have_backtrace" = "xyes"; then
- EXECINFO_LIBS="-lexecinfo"
-fi
-AC_SUBST(EXECINFO_LIBS)
+AC_SEARCH_LIBS([backtrace], [execinfo], [have_backtrace="yes"], [have_backtrace="no"])
dnl ====================================================================
dnl Check for X transport interface - allows to disable ICE Transports