More work towards a wasip3 target #1195

Job	Run time
Build only sysroot - exceptions	13m 24s
Build x86_64-windows	1h 7m 57s
Build x86_64-macos	1h 0m 56s
Build arm64-windows	1h 8m 5s
Build x86_64-linux	3m 43s
Build riscv64-linux	1h 7m 49s
Build only sysroot - default	13m 20s
Build only sysroot - static	12m 46s
Build arm64-linux	56m 37s
Build arm64-macos	1h 7m 57s
Test standalone toolchain	1s
Finalize wasi-sdk artifacts	1s
	7h 12m 36s

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