More work towards a wasip3 target #1198

Job	Run time
Build only sysroot - static	12m 13s
Build only sysroot - default	13m 36s
Build arm64-linux	22m 45s
Build arm64-macos	1h 41m 57s
Build x86_64-windows	2h 35m 29s
Build only sysroot - exceptions	13m 40s
Build x86_64-macos	1h 1m 32s
Build arm64-windows	3h 55m 3s
Build x86_64-linux	31m 52s
Build riscv64-linux	8m 6s
Finalize wasi-sdk artifacts	13m 40s
Test standalone toolchain	3m 36s
	11h 13m 29s

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