Fix undefined macro errors

src/libstore/globals.cc

@@ -209,7 +209,7 @@ StringSet Settings::getDefaultExtraPlatforms()
     StringSet levels = computeLevels();
     for (auto iter = levels.begin(); iter != levels.end(); ++iter)
         extraPlatforms.insert(*iter + "-linux");
-#elif __APPLE__
+#elif defined(__APPLE__)
     // Rosetta 2 emulation layer can run x86_64 binaries on aarch64
     // machines. Note that we can’t force processes from executing
     // x86_64 in aarch64 environments or vice versa since they can

src/libstore/unix/user-lock.cc

@@ -196,7 +196,7 @@ bool useBuildUsers()
     #ifdef __linux__
     static bool b = (settings.buildUsersGroup != "" || settings.autoAllocateUids) && isRootUser();
     return b;
-    #elif __APPLE__
+    #elif defined(__APPLE__)
     static bool b = settings.buildUsersGroup != "" && isRootUser();
     return b;
     #else

src/libutil/current-process.cc

@@ -108,7 +108,7 @@ std::optional<Path> getSelfExe()
     {
         #if defined(__linux__) || defined(__GNU__)
         return readLink("/proc/self/exe");
-        #elif __APPLE__
+        #elif defined(__APPLE__)
         char buf[1024];
         uint32_t size = sizeof(buf);
         if (_NSGetExecutablePath(buf, &size) == 0)