Why do you care about LLVM?
I think it's strange for a language to absolutely rely on the architecture of one compiler. Ideally it should have at least two that are both under FLO (free/libre/open) licenses.
Regarding LLVM specifically, see here: https://gcc.gnu.org/legacy-ml/gcc/2014-01/msg00247.html
"The nonfree compilers that are now based on LLVM prove that I was right -- that the danger was real. If I had "opened" up GCC code for use in nonfree combinations, that would not have prevented a defeat; rather, it would have caused that defeat to occur very soon.
...The existence of LLVM is a terrible setback for our community precisely because it is not copylefted and can be used as the basis for nonfree compilers -- so that all contribution to LLVM directly helps proprietary software as much as it helps us."
I'd rather just learn one thing and use it for many different projects.
1. Rather than use something like reStructuredText or Texinfo they used Markdown, and then of course had to define a bunch of custom additional stuff to make it work for documentation, plus a custom program to publish the documentation to a limited number of formats. Unlike the two documentation languages I mentioned, the Juila "customized Markdown" isn't publishable to Info, so it can't be used in Emacs: rather, it's basically just a bunch of web pages.
2. Julia is completely dependent on LLVM. Even Rust (which was initially like that) now has a GCC-based implementation.