cmake: check whether libunwind can be compiled and linked against

cmake/sdlchecks.cmake

@@ -1336,3 +1336,50 @@ macro(CheckLibUDev)
     endif()
   endif()
 endmacro()
+
+
+macro(CheckLibUnwind)
+  set(found_libunwind FALSE)
+  set(_libunwind_src "#include <libunwind.h>\nint main() {unw_context_t context; unw_getcontext(&context); return 0;}")
+
+  if(NOT found_libunwind)
+    cmake_push_check_state()
+    check_c_source_compiles("${_libunwind_src}" LIBC_HAS_WORKING_LIBUNWIND)
+    cmake_pop_check_state()
+    if(LIBC_HAS_WORKING_LIBUNWIND)
+      set(found_libunwind TRUE)
+    endif()
+  endif()
+
+  if(NOT found_libunwind)
+    cmake_push_check_state()
+    list(APPEND CMAKE_REQUIRED_LIBRARIES "unwind")
+    check_c_source_compiles("${_libunwind_src}" LIBUNWIND_HAS_WORKINGLIBUNWIND)
+    cmake_pop_check_state()
+    if(LIBUNWIND_HAS_WORKINGLIBUNWIND)
+      set(found_libunwind TRUE)
+      list(APPEND EXTRA_TEST_LIBS unwind)
+    endif()
+  endif()
+
+  if(NOT found_libunwind)
+    set(LibUnwind_PKG_CONFIG_SPEC libunwind libunwind-generic)
+    pkg_check_modules(PC_LIBUNWIND IMPORTED_TARGET ${LibUnwind_PKG_CONFIG_SPEC})
+    if(PC_LIBUNWIND_FOUND)
+      cmake_push_check_state()
+      list(APPEND CMAKE_REQUIRED_LIBRARIES ${PC_LIBUNWIND_LIBRARIES})
+      list(APPEND CMAKE_REQUIRED_INCLUDES ${PC_LIBUNWIND_INCLUDE_DIRS})
+      check_c_source_compiles("${_libunwind_src}" PC_LIBUNWIND_HAS_WORKING_LIBUNWIND)
+      cmake_pop_check_state()
+      if(PC_LIBUNWIND_HAS_WORKING_LIBUNWIND)
+        set(found_libunwind TRUE)
+        list(APPEND EXTRA_TEST_LIBS ${PC_LIBUNWIND_LIBRARIES})
+        list(APPEND EXTRA_TEST_INCLUDES ${PC_LIBUNWIND_INCLUDE_DIRS})
+      endif()
+    endif()
+  endif()
+
+  if(found_libunwind)
+    set(HAVE_LIBUNWIND_H TRUE)
+  endif()
+endmacro()