## Summary
- Adds birthtime (file creation time) support on Linux using the `statx`
syscall
- Stores birthtime in architecture-specific unused fields of the kernel
Stat struct (x86_64 and aarch64)
- Falls back to traditional `stat` on kernels < 4.11 that don't support
`statx`
- Includes comprehensive tests validating birthtime behavior
Fixes#6585
## Implementation Details
**src/sys.zig:**
- Added `StatxField` enum for field selection
- Implemented `statxImpl()`, `fstatx()`, `statx()`, and `lstatx()`
functions
- Stores birthtime in unused padding fields (architecture-specific for
x86_64 and aarch64)
- Graceful fallback to traditional stat if statx is not supported
**src/bun.js/node/node_fs.zig:**
- Updated `stat()`, `fstat()`, and `lstat()` to use statx functions on
Linux
**src/bun.js/node/Stat.zig:**
- Added `getBirthtime()` helper to extract birthtime from
architecture-specific storage
**test/js/node/fs/fs-birthtime-linux.test.ts:**
- Tests non-zero birthtime values
- Verifies birthtime immutability across file modifications
- Validates consistency across stat/lstat/fstat
- Tests BigInt stats with nanosecond precision
- Verifies birthtime ordering relative to other timestamps
## Test Plan
- [x] Run `bun bd test test/js/node/fs/fs-birthtime-linux.test.ts` - all
5 tests pass
- [x] Compare behavior with Node.js - identical behavior
- [x] Compare with system Bun - system Bun returns epoch, new
implementation returns real birthtime
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---------
Co-authored-by: Claude Bot <claude-bot@bun.sh>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
