Makefile: Allow building libquickjs as a shared library

[lanodan]

Adapted from https://git.alpinelinux.org/aports/tree/community/quickjs/01-sharedlib.patch?id=27a8f649949c36bfc3e45854e08c48a8eb06e07c

Co-Authored-By: Celeste 20312-Celeste@users.gitlab.alpinelinux.org

[nickva]

FYI: #195

[lanodan]

If the issue is ABI versioning/stability, it shouldn't be a problem here because it doesn't introduces it. The SONAME includes the version, so on linking with current version the NEEDED entry ends up being `libquickjs.so.2024.01.13`.

[nickva]

@lanodan np, I personally wouldn't mind having an .so version as well, was just highlighting that it was brought up before in the context of this project.

Also, the friendly fork quickjs-ng seems to support it https://github.com/quickjs-ng/quickjs/blob/0de570988a0decf7676ebcc831817fc844746bac/CMakeLists.txt#L86

[kapouer]

Note that abigail-tools are very easy to use to track ABI changes.
One just has to run that script and keep the generated abi.xml file
in the repository.

set -xe
abidw --header-file $(headerPath) $(libPath) > $(abiPath).new
if [ -f $(abiPath) ]; then
  abidiff $(abiPath) $(abiPath).new
fi
mv $(abiPath).new $(abiPath)