Fix calling custom call conv functions from inline asm #1727

Job	Run time
abi_cafe (ubuntu-24.04-arm, aarch64-unknown-linux-gnu)	2m 2s
abi_cafe (macos-15-intel, x86_64-apple-darwin)	2m 5s
abi_cafe (ubuntu-latest, x86_64-unknown-linux-gnu)	2m 6s
abi_cafe (macos-latest, aarch64-apple-darwin)	2m 10s
abi_cafe (windows-latest, x86_64-pc-windows-msvc)	2m 5s
	10m 28s

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