android: Make libbacktrace optional again

For the same reason why we used to have USE_LIBBACKTRACE with the old
Android makefiles, allow to build Mesa without linking to it.

In recent VNDK versions, libbacktrace isn't available.

When building without linking libbacktrace, for some reason some symbols
related to C++ exception handling are exposed. Allow them in the symbols
check script.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Signed-off-by: Helen Koike <helen.koike@collabora.com>
Reviewed-by: Sergi Blanch Torné <sergi.blanch.torne@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20019>

src/util/u_debug_stack_android.cpp

@@ -21,11 +21,14 @@
  * IN THE SOFTWARE.
  */
 
+#include "u_debug_stack.h"
+
+#if WITH_LIBBACKTRACE
+
 #include <backtrace/Backtrace.h>
 
 #include "util/simple_mtx.h"
 #include "util/u_debug.h"
-#include "u_debug_stack.h"
 #include "util/hash_table.h"
 #include "util/u_thread.h"
 
@@ -120,3 +123,27 @@ debug_backtrace_print(FILE *f,
                  backtrace[i].off);
    }
 }
+
+#else
+
+void
+debug_backtrace_capture(debug_stack_frame *backtrace,
+                        unsigned start_frame,
+                        unsigned nr_frames)
+{
+}
+
+void
+debug_backtrace_dump(const debug_stack_frame *backtrace,
+                     unsigned nr_frames)
+{
+}
+
+void
+debug_backtrace_print(FILE *f,
+                      const debug_stack_frame *backtrace,
+                      unsigned nr_frames)
+{
+}
+
+#endif // WITH_LIBBACKTRACE