fuse integration: add POSIX compliance test suite

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

test/fuse_integration/sendfile_linux.go

@@ -0,0 +1,33 @@
+//go:build linux
+
+package fuse
+
+import (
+	"syscall"
+	"unsafe"
+)
+
+// Sendfile support for Linux
+
+func sendfileTransfer(outFd int, inFd int, offset *int64, count int) (int, error) {
+	var offsetPtr uintptr
+	if offset != nil {
+		offsetPtr = uintptr(unsafe.Pointer(offset))
+	}
+
+	n, _, errno := syscall.Syscall6(syscall.SYS_SENDFILE,
+		uintptr(outFd),
+		uintptr(inFd),
+		offsetPtr,
+		uintptr(count),
+		0, 0)
+
+	if errno != 0 {
+		return 0, errno
+	}
+	return int(n), nil
+}
+
+func isSendfileSupported() bool {
+	return true
+}