configure.ac: Use LIBS rather than LDFLAGS to add -ldl to dladdr check

ec8ebff "Check for dladdr()" erroneously uses LDFLAGS rather than LIBS to add
-ldl to the dladdr check.

Replace the workaround in 39a4cc4 of explicitly checking in libdl, with a more
correct approach of using LIBS.

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Tested-by: Pali Rohár <pali.rohar@gmail.com>
Cc: "10.2" <mesa-stable@lists.freedesktop.org>

configure.ac

@@ -535,9 +535,10 @@ AC_CHECK_FUNC([dlopen], [DEFINES="$DEFINES -DHAVE_DLOPEN"],
 AC_SUBST([DLOPEN_LIBS])
 
 dnl Check if that library also has dladdr
-AC_CHECK_FUNC([dladdr], [DEFINES="$DEFINES -DHAVE_DLADDR"],
-    [AC_CHECK_LIB([dl], [dladdr],
-       [DEFINES="$DEFINES -DHAVE_DLADDR"])])
+save_LIBS="$LIBS"
+LIBS="$LIBS $DLOPEN_LIBS"
+AC_CHECK_FUNCS([dladdr])
+LIBS="$save_LIBS"
 
 case "$host_os" in
 darwin*|mingw*)