when building doc, this warning is displayed, even if libcurl is found earlier
on Windows and on linux
This warning means muon was compiled without libcurl support, but a function requiring libcurl was called. It is unrelated to whether or not libcurl was found via
dependency(). In your specific case, you probably compiled muon without libcurl (if you just did ./bootstrap.sh, then this is always the case), then tried to configure muon with docs enabled, which in turn tried to get the meson-docs wrap via curl and failed, printing the warning you mentioned.