This is a Lua module so it should be multi-impl, that said upstream build infrastructure implicitly assumes single-impl (by default it doesn't install headers and libraries into implementation-specific directories and its pkgconfig file is unversioned).
Path-of-least-resistance single-impl version in commit 40ae837172c06f2e9532db2b7ee570b966e4e6fb, multi-impl version in commit f12b6a56bef830507569b5c1a54baf234b861fa1.
Works with lua5.4 now too, the only thing that needed to be changed was that lua-compat-5.3 has only supported that version since 0.9.
