fuse integration: add POSIX compliance test suite

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test/fuse_integration/sendfile_unsupported.go

@@ -0,0 +1,19 @@
+//go:build !linux && !darwin
+
+package fuse
+
+import (
+	"errors"
+)
+
+// Sendfile support for unsupported platforms
+
+var ErrSendfileNotSupported = errors.New("sendfile not supported on this platform")
+
+func sendfileTransfer(outFd int, inFd int, offset *int64, count int) (int, error) {
+	return 0, ErrSendfileNotSupported
+}
+
+func isSendfileSupported() bool {
+	return false
+}