macos

Allow read-only methods to work against a frozen StringIO #427

Job	Run time
ruby-versions / Generate Ruby versions	2s
macos-13 2.7	54s
macos-13 3.0	18s
macos-13 3.1	24s
macos-13 3.2	22s
macos-13 3.3	22s
macos-13 3.4	23s
macos-13 debug	26s
macos-13 head	23s
macos-14 2.7	32s
macos-14 3.0	14s
macos-14 3.1	14s
macos-14 3.2	16s
macos-14 3.3	13s
macos-14 3.4	13s
macos-14 debug	21s
macos-14 head	15s
	5m 52s

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