build: remove duplicate visibility attribute detection

We are already testing for this, and our test works correctly with a Darwin
target, where the macro does not. Darwin targets do not support "protected"
visibility.

Author: fanquake

configure.ac

@@ -813,7 +813,6 @@ if test x$ac_cv_sys_large_files != x &&
   CPPFLAGS="$CPPFLAGS -D_LARGE_FILES=$ac_cv_sys_large_files"
 fi
 
-AX_GCC_FUNC_ATTRIBUTE([visibility])
 AX_GCC_FUNC_ATTRIBUTE([dllexport])
 AX_GCC_FUNC_ATTRIBUTE([dllimport])
 
@@ -984,13 +983,13 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
  [ AC_MSG_RESULT(no)]
 )
 
-AC_MSG_CHECKING([for visibility attribute])
-AC_LINK_IFELSE([AC_LANG_SOURCE([
-  int foo_def( void ) __attribute__((visibility("default")));
+AC_MSG_CHECKING([for default visibility attribute])
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([
+  int foo(void) __attribute__((visibility("default")));
   int main(){}
   ])],
   [
-    AC_DEFINE(HAVE_VISIBILITY_ATTRIBUTE,1,[Define if the visibility attribute is supported.])
+    AC_DEFINE(HAVE_DEFAULT_VISIBILITY_ATTRIBUTE,1,[Define if the visibility attribute is supported.])
     AC_MSG_RESULT(yes)
   ],
   [

src/script/bitcoinconsensus.h

@@ -18,7 +18,7 @@
         #define EXPORT_SYMBOL
       #endif
     #endif
-  #elif defined(HAVE_FUNC_ATTRIBUTE_VISIBILITY)
+  #elif defined(HAVE_DEFAULT_VISIBILITY_ATTRIBUTE)
     #define EXPORT_SYMBOL __attribute__ ((visibility ("default")))
   #endif
 #elif defined(MSC_VER) && !defined(STATIC_LIBBITCOINCONSENSUS)