Fix CMake Script for libunwind Feature Check

Fix CMake Script for libunwind Feature Check

Check the availability correctly for Linux.

The cmake configuration script has been trying to find out
the availability of functions directly with check_function_exists,
which depends on the symbol names in .so files.
However, the libunwind implementation uses macros to
redefine functions names for each architecture making it
impossible to directly look up symbol tables of .so files.

In order to allow the script to use the information in
header files, check_function_exists should be replaced
with check_cxx_source_compiles.

Besides config.h.in had missing declarations for the
CMAKE variables

Fix #3372

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>