autotools: improve libunwind detection

Libuwind may not be shipped with a pkg-config file.
It can be distributed on the system, but the autotools
would fail to detect it because it relied only on pkg-config.

We now first check with pkg-config, and then try to compile and
link a program using libuwind to see if it is supported anyway.

This is a first step towards a working eina_log_backtrace on
Mac OS X.

diff --git a/Makefile.am b/Makefile.am
index 1efae6e..f966432 100644 (file)
--- a/Makefile.am
+++ b/Makefile.am
@@ -42,6 +42,7 @@ m4/efl_compiler.m4 \
 m4/efl_doxygen.m4 \
 m4/efl_path_max.m4 \
 m4/efl_threads.m4 \
+m4/efl_libunwind.m4 \
 m4/eina_check.m4 \
 m4/eina_config.m4 \
 m4/eio_check_options.m4 \