[gnome-keyring] Look for both dlopen and dlsym when configuring

[Stefan Walter <stefw src gnome org>]

commit 4e6eca91e13edcfda811f89c994ee723744afed6
Author: Iain Lane <iain orangesquash org uk>
Date:   Tue May 10 12:11:31 2016 +0100

    Look for both dlopen and dlsym when configuring
    
    We use both, and they may not both be exposed by libc but by libdl
    instead.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=766221

 configure.ac |   25 ++++++++++++++++++++-----
 1 files changed, 20 insertions(+), 5 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 629f545..9060929 100644
--- a/configure.ac
+++ b/configure.ac
@@ -263,11 +263,26 @@ fi
 # --------------------------------------------------------------------
 # Find DL functionality
 
-AC_CHECK_LIB(c, dlopen, DL_LIBS="",
-       AC_CHECK_LIB(dl, dlopen, DL_LIBS="-ldl",
-               AC_MSG_ERROR([Could not find a library with the dlopen function])
-       )
-)
+dnl *** dlopen() and dlsym() in system libraries
+AS_IF([ test -z "$HAVE_DL"], [
+       AC_CHECK_FUNC(dlopen,
+                     [AC_CHECK_FUNC(dlsym,
+                                    [HAVE_DL=c],[])],
+                     [])
+])
+
+dnl *** dlopen() and dlsym() in libdl
+AS_IF([ test -z "$HAVE_DL"], [
+       AC_CHECK_LIB(dl, dlopen,
+                    [AC_CHECK_LIB(dl, dlsym,
+                                  [DL_LIBS=-ldl
+                                  HAVE_DL=dl],[])],
+                    [])
+])
+
+AS_IF([ test -z "$HAVE_DL"], [
+       AC_MSG_ERROR([Could not find a library with the dlopen and dlsym functions])
+])
 
 AC_SUBST(DL_LIBS)