When testing variants in the libmongoc-version axis, a different libmongoc branch is checked out in the existing submodule. While make libmongoc-version-current is executed, the source lists in config.m4 and config.w32 are not. This poses a problem when files differ between branches. For example, mongo-shared.c was introduced in 1.20-dev and does not exist in 1.19.x.

There are several possible solutions:

• Forgo checking out submodules and instead install custom libmongoc versions as system libraries. This would have the benefit of granting test coverage for the mongodb-system-libs configure option.

• Create a script that updates the various source lists in config.m4 and config.w32. Such a script would also prove useful when manually updating the libmongoc submodule (similar to why make libmongoc-version-current was created).