chore(build) add define to build without expat_config.h

[Tieske]

Workaround for #32

When building the lib and the header expat_config.h is not being found, then the system is missing an important header. The settings in that header file can change the ABI of the compiled lib, hence the header is required to have.

Since on some systems/package managers the header is not included here's a workaround;

1. ensure you have libExpat 2.4+
2. try building the library
3. try building while defining LUAEXPAT_SKIP_DTD_SUPPORT and XML_DTD (include DTD support)
4. try building while defining LUAEXPAT_SKIP_DTD_SUPPORT (disable DTD support)

To build with LuaRocks you need to pull a trick since LuaRocks does not have a way to pass the defines via the command line. Instead you can override the CC setting and include the defines, like this:

luarocks install luaexpat CC="gcc -DLUAEXPAT_SKIP_DTD_SUPPORT -DXML_DTD"

[Tieske]

@alerque can you give this workaround a try to see if it fixes your issue?

[Tieske]

while unreleased, you'll have to checkout this branch and do the following from the repo;

luarocks make CC="gcc -DLUAEXPAT_SKIP_DTD_SUPPORT -DXML_DTD"

[alerque]

I'll look into it. I think the issue surfaced in Homebrew builds for another project for me, I'll have to try to figure out how to replicate that.

[Tieske]

@alerque not sure, but I think this one: Homebrew/homebrew-core#114831