FreeBSD compability (#57)

diff --git a/absl/debugging/internal/stacktrace_config.h b/absl/debugging/internal/stacktrace_config.h
index 57f0b0f..9bd2a2a 100644
--- a/absl/debugging/internal/stacktrace_config.h
+++ b/absl/debugging/internal/stacktrace_config.h
@@ -25,8 +25,8 @@
 #if ABSL_STACKTRACE_INL_HEADER
 #error ABSL_STACKTRACE_INL_HEADER cannot be directly set
 #elif defined(__native_client__) || defined(__APPLE__) || \
-    defined(__ANDROID__) || defined(__myriad2__) || defined(asmjs__) || \
-    defined(__Fuchsia__)
+    defined(__FreeBSD__) || defined(__ANDROID__) || defined(__myriad2__) || \
+    defined(asmjs__) || defined(__Fuchsia__)
 #define ABSL_STACKTRACE_INL_HEADER \
     "absl/debugging/internal/stacktrace_unimplemented-inl.inc"