Make empty PT2 wrapper TUs byte-distinct per optimizer #9141

Job	Run time
build_artifact (x86, linux.4xlarge, 3.14, gcc)	4m 6s
build_artifact (arm, linux.arm64.m7g.4xlarge, 3.14, gcc)	3m 34s
benchmark_artifact (arm, linux.arm64.m7g.4xlarge, 30, 3.14, gcc)	1m 12s
benchmark_artifact (x86, linux.4xlarge, 20, 3.14, gcc)	1m 18s
	10m 10s

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