check for LIBUNWIND_HAS_UNW_CACHE_PER_THREAD before usage

Apparently this isn't available on freebsd

cmake/FindLibunwind.cmake

@@ -60,6 +60,7 @@ if (LIBUNWIND_LIBRARY)
   check_c_source_compiles("#define UNW_LOCAL_ONLY 1\n#include <libunwind.h>\nint main() { void* buf[10]; unw_backtrace(&buf, 10); return 0; }" LIBUNWIND_HAS_UNW_BACKTRACE)
   check_c_source_compiles ("#define UNW_LOCAL_ONLY 1\n#include <libunwind.h>\nint main() { void* buf[10]; unw_backtrace_skip(&buf, 10, 2); return 0; }" LIBUNWIND_HAS_UNW_BACKTRACE_SKIP)
   check_c_source_compiles ("#define UNW_LOCAL_ONLY 1\n#include <libunwind.h>\nint main() { return unw_set_cache_size(unw_local_addr_space, 1024, 0); }" LIBUNWIND_HAS_UNW_SET_CACHE_SIZE)
+  check_c_source_compiles ("#define UNW_LOCAL_ONLY 1\n#include <libunwind.h>\nint main() { return unw_set_caching_policy(unw_local_addr_space, UNW_CACHE_PER_THREAD); }" LIBUNWIND_HAS_UNW_CACHE_PER_THREAD)
   set(CMAKE_REQUIRED_QUIET ${CMAKE_REQUIRED_QUIET_SAVE})
   set(CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES_SAVE})
   set(CMAKE_REQUIRED_INCLUDES ${CMAKE_REQUIRED_INCLUDES_SAVE})

src/track/trace_libunwind.cpp

@@ -49,9 +49,12 @@ void Trace::print()
 void Trace::setup()
 {
     // configure libunwind for better speed
+#if LIBUNWIND_HAS_UNW_CACHE_PER_THREAD
     if (unw_set_caching_policy(unw_local_addr_space, UNW_CACHE_PER_THREAD)) {
         fprintf(stderr, "WARNING: Failed to enable per-thread libunwind caching.\n");
     }
+#endif
+
 #if LIBUNWIND_HAS_UNW_SET_CACHE_SIZE
     if (unw_set_cache_size(unw_local_addr_space, 1024, 0)) {
         fprintf(stderr, "WARNING: Failed to set libunwind cache size.\n");

src/util/libunwind_config.h.cmake

@@ -17,5 +17,7 @@
 
 #cmakedefine01 LIBUNWIND_HAS_UNW_SET_CACHE_SIZE
 
+#cmakedefine01 LIBUNWIND_HAS_UNW_CACHE_PER_THREAD
+
 #endif // LIBUNWIND_CONFIG_H