Create libwasmvmstatic for macOS

[webmaster128]

• Add experimental libwasmvmstatic support macOS (#387)
• Move build_macos_static.sh into builder image and remove the mounting -v $(shell pwd)/builders/guest/build_macos_static.sh:/usr/local/bin/build_macos_static.sh (#411)
• Remove muslc example in favour of the new wasmvmstatic example (#438)
• Update build matrix in https://github.com/CosmWasm/wasmvm/blob/main/docs/libwasmvm_builds.py / README.md