Fixes to enable building for Wasm targets #149

Job	Run time
Extension template / Generate matrix	3s
Rust builds (using Delta extension) / Generate matrix	11s
Extension template / Windows (windows_amd64, x64-windows-static-md)	1m 10s
Extension template / MacOS (osx_amd64, x86_64, x64-osx)	1m 32s
Extension template / Windows (windows_amd64_rtools, x64-mingw-static)	1m 13s
Extension template / DuckDB-Wasm (wasm_mvp, wasm32-emscripten)	1m 13s
Extension template / MacOS (osx_arm64, arm64, arm64-osx)	1m 31s
Extension template / DuckDB-Wasm (wasm_eh, wasm32-emscripten)	1m 32s
Extension template / DuckDB-Wasm (wasm_threads, wasm32-emscripten)	1m 31s
Extension template / Linux (linux_amd64, ubuntu:18.04, x64-linux)	1m 26s
Extension template / Linux (linux_amd64_gcc4, quay.io/pypa/manylinux2014_x86_64, x64-linux)	1m 26s
Extension template / Linux (linux_arm64, ubuntu:18.04, arm64-linux)	1m 26s
Rust builds (using Delta extension) / DuckDB-Wasm	0s
Rust builds (using Delta extension) / Linux (linux_amd64, ubuntu:18.04, x64-linux)	1m 2s
Rust builds (using Delta extension) / MacOS (osx_amd64, x86_64, x64-osx)	1m 9s
Rust builds (using Delta extension) / Windows	0s
Rust builds (using Delta extension) / Linux (linux_amd64_gcc4, quay.io/pypa/manylinux2014_x86_64, x64-linux)	1m 15s
Rust builds (using Delta extension) / MacOS (osx_arm64, arm64, arm64-osx)	1m 21s
Rust builds (using Delta extension) / Linux (linux_arm64, ubuntu:18.04, arm64-linux)	1m 16s
	20m 17s

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