HAVE_SYNC_FILE_RANGE should be protected by ifdef __linux__.

Related to issue #2372.

src/config.h

@@ -91,6 +91,7 @@
 
 /* Define rdb_fsync_range to sync_file_range() on Linux, otherwise we use
  * the plain fsync() call. */
+#ifdef __linux__
 #if defined(__GLIBC__) && defined(__GLIBC_PREREQ)
 #if (LINUX_VERSION_CODE >= 0x020611 && __GLIBC_PREREQ(2, 6))
 #define HAVE_SYNC_FILE_RANGE 1
@@ -100,6 +101,7 @@
 #define HAVE_SYNC_FILE_RANGE 1
 #endif
 #endif
+#endif
 
 #ifdef HAVE_SYNC_FILE_RANGE
 #define rdb_fsync_range(fd,off,size) sync_file_range(fd,off,size,SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE)