build: Replace MAC_OSX macro with existing __APPLE__

Adopting `__APPLE__` aligns our project with broader industry practices, including those in prominent projects such as the Linux kernel (and even our own code).

See: https://sourceforge.net/p/predef/wiki/OperatingSystems/#macos

CMakeLists.txt

@@ -324,10 +324,7 @@ if (CMAKE_SYSTEM_NAME STREQUAL "Linux" AND CMAKE_SIZEOF_VOID_P EQUAL 4)
 endif()
 
 if(CMAKE_SYSTEM_NAME STREQUAL "Darwin")
-  target_compile_definitions(core_interface INTERFACE
-    MAC_OSX
-    OBJC_OLD_DISPATCH_PROTOTYPES=0
-  )
+  target_compile_definitions(core_interface INTERFACE OBJC_OLD_DISPATCH_PROTOTYPES=0)
   # These flags are specific to ld64, and may cause issues with other linkers.
   # For example: GNU ld will interpret -dead_strip as -de and then try and use
   # "ad_strip" as the symbol for the entry point.

src/common/args.cpp

@@ -184,7 +184,7 @@ bool ArgsManager::ParseParameters(int argc, const char* const argv[], std::strin
     for (int i = 1; i < argc; i++) {
         std::string key(argv[i]);
 
-#ifdef MAC_OSX
+#ifdef __APPLE__
         // At the first time when a user gets the "App downloaded from the
         // internet" warning, and clicks the Open button, macOS passes
         // a unique process serial number (PSN) as -psn_... command-line
@@ -741,7 +741,7 @@ fs::path GetDefaultDataDir()
         pathRet = fs::path("/");
     else
         pathRet = fs::path(pszHome);
-#ifdef MAC_OSX
+#ifdef __APPLE__
     // macOS
     return pathRet / "Library/Application Support/Bitcoin";
 #else

src/common/system.cpp

@@ -70,7 +70,7 @@ void SetupEnvironment()
 #endif
     // On most POSIX systems (e.g. Linux, but not BSD) the environment's locale
     // may be invalid, in which case the "C.UTF-8" locale is used as fallback.
-#if !defined(WIN32) && !defined(MAC_OSX) && !defined(__FreeBSD__) && !defined(__OpenBSD__) && !defined(__NetBSD__)
+#if !defined(WIN32) && !defined(__APPLE__) && !defined(__FreeBSD__) && !defined(__OpenBSD__) && !defined(__NetBSD__)
     try {
         std::locale(""); // Raises a runtime error if current locale is invalid
     } catch (const std::runtime_error&) {

src/random.cpp

@@ -34,7 +34,7 @@
 #include <sys/time.h>
 #endif
 
-#if defined(HAVE_GETRANDOM) || (defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX))
+#if defined(HAVE_GETRANDOM) || (defined(HAVE_GETENTROPY_RAND) && defined(__APPLE__))
 #include <sys/random.h>
 #endif
 
@@ -387,7 +387,7 @@ void GetOSRand(unsigned char *ent32)
        The function call is always successful.
      */
     arc4random_buf(ent32, NUM_OS_RANDOM_BYTES);
-#elif defined(HAVE_GETENTROPY_RAND) && defined(MAC_OSX)
+#elif defined(HAVE_GETENTROPY_RAND) && defined(__APPLE__)
     if (getentropy(ent32, NUM_OS_RANDOM_BYTES) != 0) {
         RandFailure();
     }

src/util/fs_helpers.cpp

@@ -117,7 +117,7 @@ bool FileCommit(FILE* file)
         LogPrintf("FlushFileBuffers failed: %s\n", Win32ErrorString(GetLastError()));
         return false;
     }
-#elif defined(MAC_OSX) && defined(F_FULLFSYNC)
+#elif defined(__APPLE__) && defined(F_FULLFSYNC)
     if (fcntl(fileno(file), F_FULLFSYNC, 0) == -1) { // Manpage says "value other than -1" is returned on success
         LogPrintf("fcntl F_FULLFSYNC failed: %s\n", SysErrorString(errno));
         return false;
@@ -195,7 +195,7 @@ void AllocateFileRange(FILE* file, unsigned int offset, unsigned int length)
     nFileSize.u.HighPart = nEndPos >> 32;
     SetFilePointerEx(hFile, nFileSize, 0, FILE_BEGIN);
     SetEndOfFile(hFile);
-#elif defined(MAC_OSX)
+#elif defined(__APPLE__)
     // OSX specific version
     // NOTE: Contrary to other OS versions, the OSX version assumes that
     // NOTE: offset is the size of the file.

src/util/threadnames.cpp

@@ -29,7 +29,7 @@ static void SetThreadName(const char* name)
     ::prctl(PR_SET_NAME, name, 0, 0, 0);
 #elif (defined(__FreeBSD__) || defined(__OpenBSD__) || defined(__DragonFly__))
     pthread_set_name_np(pthread_self(), name);
-#elif defined(MAC_OSX)
+#elif defined(__APPLE__)
     pthread_setname_np(name);
 #else
     // Prevent warnings for unused parameters...