fs: expose frsize field in statfs #4890

Job	Run time
Build slim tarball	2m 25s
aarch64-darwin: with shared libraries	18m 21s
x86_64-linux: with shared libraries	22m 42s
aarch64-linux: with shared libraries	19m 4s
x86_64-darwin: with shared libraries	33m 3s
	1h 35m 35s

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