util: Refactor FileCommit from an #if sequence nested in #else, to a sequence of #elif

This should not change the actual code generation.

Author: eklitzke

src/util/system.cpp

@@ -1024,23 +1024,21 @@ bool FileCommit(FILE *file)
         LogPrintf("%s: FlushFileBuffers failed: %d\n", __func__, GetLastError());
         return false;
     }
-#else
-    #if HAVE_FDATASYNC
+#elif HAVE_FDATASYNC
     if (fdatasync(fileno(file)) != 0 && errno != EINVAL) { // Ignore EINVAL for filesystems that don't support sync
         LogPrintf("%s: fdatasync failed: %d\n", __func__, errno);
         return false;
     }
-    #elif defined(MAC_OSX) && defined(F_FULLFSYNC)
+#elif defined(MAC_OSX) && defined(F_FULLFSYNC)
     if (fcntl(fileno(file), F_FULLFSYNC, 0) == -1) { // Manpage says "value other than -1" is returned on success
         LogPrintf("%s: fcntl F_FULLFSYNC failed: %d\n", __func__, errno);
         return false;
     }
-    #else
+#else
     if (fsync(fileno(file)) != 0 && errno != EINVAL) {
         LogPrintf("%s: fsync failed: %d\n", __func__, errno);
         return false;
     }
-    #endif
 #endif
     return true;
 }