Merge bitcoin/bitcoin#23555: util: Add missing fstatfs to syscall sandbox

fade4b3 util: Add missing fstatfs to syscall sandbox (MarcoFalke)

Pull request description:

  Looks like this is used by boost 1.77 in `./test/functional/wallet_backup.py --descriptors`.

  Fixes bitcoin/bitcoin#23554

ACKs for top commit:
  fanquake:
    ACK fade4b3 - reproduced the failure on Tumbleweed:

Tree-SHA512: cd7381e87c7cb4596da0b9e36c8776a3ef19f5aeb29ee9db1867657c4c1f071485ffea0fba0af950f10a16a8bdb0a0c70ffcc5be802e82d60882e00f7d2009ac

Author: fanquake

src/util/syscall_sandbox.cpp

@@ -581,14 +581,15 @@ class SeccompPolicyBuilder
         allowed_syscalls.insert(__NR_fdatasync);       // synchronize a file's in-core state with storage device
         allowed_syscalls.insert(__NR_flock);           // apply or remove an advisory lock on an open file
         allowed_syscalls.insert(__NR_fstat);           // get file status
-        allowed_syscalls.insert(__NR_newfstatat);      // get file status
+        allowed_syscalls.insert(__NR_fstatfs);         // get file system status
         allowed_syscalls.insert(__NR_fsync);           // synchronize a file's in-core state with storage device
         allowed_syscalls.insert(__NR_ftruncate);       // truncate a file to a specified length
         allowed_syscalls.insert(__NR_getcwd);          // get current working directory
         allowed_syscalls.insert(__NR_getdents);        // get directory entries
         allowed_syscalls.insert(__NR_getdents64);      // get directory entries
         allowed_syscalls.insert(__NR_lstat);           // get file status
         allowed_syscalls.insert(__NR_mkdir);           // create a directory
+        allowed_syscalls.insert(__NR_newfstatat);      // get file status
         allowed_syscalls.insert(__NR_open);            // open and possibly create a file
         allowed_syscalls.insert(__NR_openat);          // open and possibly create a file
         allowed_syscalls.insert(__NR_readlink);        // read value of a symbolic link