Merge #19614: util: use HAVE_FDATASYNC to determine fdatasync() use

1d8338d util: use HAVE_FDATASYNC to determine fdatasync() use (fanquake)

Pull request description:

  Rather than just using on Linux and NetBSD, use `fdatasync()` based
  on whether it's available. i.e `fdatasync` is available in newer versions of FreeBSD.

  This also aligns more closely with what is being done in leveldb.

  Was pointed out by Luke in #19430.

ACKs for top commit:
  practicalswift:
    ACK 1d8338d -- patch looks correct
  laanwj:
    ACK 1d8338d
  hebasto:
    ACK 1d8338d

Tree-SHA512: 7dd6d87f5dc0c0ba21ae42f96b63fc12b34806cd536457fc4284f14bb8c235765344be228b000c6adf4cd1e8c4e6a03a18ca18ab22599c42cc3b706e0bcd1a17

Author: laanwj

src/util/system.cpp

@@ -1025,7 +1025,7 @@ bool FileCommit(FILE *file)
         return false;
     }
 #else
-    #if defined(__linux__) || defined(__NetBSD__)
+    #if defined(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;