configure.ac: add `-funwind-tables` to work around clang bug

Replaces the workaround from commit
751fff07fb which fixed only one of many
crash locations.

See:

 https://github.com/MusicPlayerDaemon/MPD/issues/373
 https://github.com/android-ndk/ndk/issues/831
 https://bugs.llvm.org/show_bug.cgi?id=32611

configure.ac

@@ -1354,6 +1354,11 @@ AX_APPEND_COMPILE_FLAGS([-fno-threadsafe-statics])
 AX_APPEND_COMPILE_FLAGS([-fmerge-all-constants])
 AX_APPEND_COMPILE_FLAGS([-ffast-math])
 AX_APPEND_COMPILE_FLAGS([-ftree-vectorize])
+
+dnl Workaround for clang bug
+dnl https://bugs.llvm.org/show_bug.cgi?id=32611
+AX_APPEND_COMPILE_FLAGS([-funwind-tables])
+
 AC_LANG_POP
 
 dnl ---------------------------------- debug ----------------------------------

src/input/Error.hxx

@@ -30,15 +30,7 @@
  * exist?  This function attempts to recognize exceptions thrown by
  * various input plugins.
  */
-#ifndef __clang__
-/* the "pure" attribute must be disabled because it triggers a clang
-   bug, wrongfully leading to std::terminate() even though the
-   function catches all exceptions thrown by std::rethrow_exception();
-   this can be reproduced with clang 7 from Android NDK r18b and on
-   clang 6 on FreeBSD
-   (https://github.com/MusicPlayerDaemon/MPD/issues/373) */
 gcc_pure
-#endif
 bool
 IsFileNotFound(std::exception_ptr e);