build_configs: remove `HAVE_LIBUNWIND_H`

It is only used in SDL_test, which does not use the config header.

include/build_config/SDL_build_config.h.cmake

@@ -50,7 +50,6 @@
 #cmakedefine HAVE_ALLOCA_H 1
 #cmakedefine HAVE_ICONV_H 1
 #cmakedefine HAVE_INTTYPES_H 1
-#cmakedefine HAVE_LIBUNWIND_H 1
 #cmakedefine HAVE_LIMITS_H 1
 #cmakedefine HAVE_MALLOC_H 1
 #cmakedefine HAVE_MATH_H 1

include/build_config/SDL_build_config_macos.h

@@ -34,7 +34,6 @@
 #define HAVE_ALLOCA_H 1
 #define HAVE_FLOAT_H 1
 #define HAVE_INTTYPES_H 1
-#define HAVE_LIBUNWIND_H 1
 #define HAVE_LIMITS_H 1
 #define HAVE_MATH_H 1
 #define HAVE_SIGNAL_H 1