wazevo: handle empty host module #4052

Job	Run time
Build TinyGo test binary	11s
Build Zig test binary	5s
Go-1.21 (Ubuntu, amd64, baseline)	6m 45s
Go-1.22 (Ubuntu, amd64, baseline)	6m 33s
libsodium (Ubuntu, amd64, optimizing)	6m 36s
Go-1.21 (macOS, amd64, baseline)	7m 8s
libsodium (macOS, arm64, optimizing)	26s
wasi-testsuite (ubuntu-22.04)	22s
Go-1.22 (macOS, amd64, baseline)	7m 47s
wasi-testsuite (macos-12)	1m 16s
Go-1.21 (Windows, amd64, baseline)	7m 30s
wasi-testsuite (windows-2022)	2m 11s
Go-1.22 (Windows, amd64, baseline)	7m 31s
Go-1.21 (macOS, arm64, optimizing)	8m 22s
Go-1.22 (macOS, arm64, optimizing)	9m 45s
Go-1.21 (Ubuntu, amd64, optimizing)	9m 47s
Go-1.22 (Ubuntu, amd64, optimizing)	10m 42s
Zig (Ubuntu, amd64, baseline)	4m 8s
Zig (macOS, amd64, baseline)	8m 25s
Zig (Windows, amd64, baseline)	7m 15s
Zig (macOS, arm64, optimizing)	1m 35s
Zig (Ubuntu, amd64, optimizing)	1m 56s
TinyGo (Ubuntu, amd64, baseline)	1m 57s
TinyGo (macOS, amd64, baseline)	2m 42s
TinyGo (Windows, amd64, baseline)	3m 26s
TinyGo (macOS, arm64, optimizing)	2m 55s
TinyGo (Ubuntu, amd64, optimizing)	2m 39s
	2h 9m 55s

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