Description of problem:
Currently, EPEL7 has CMake 3.17.5. This won't be sufficient for building new versions of LLVM, which is warning since https://reviews.llvm.org/D137724

if ("${CMAKE_VERSION}" VERSION_LESS "3.20.0")
  message(WARNING
    "Your CMake version is ${CMAKE_VERSION}. Starting with LLVM 17.0.0, the "
    "minimum version of CMake required to build LLVM will become 3.20.0, and "
    "using an older CMake will become an error. Please upgrade your CMake to "
    "at least 3.20.0 now to avoid issues in the future!")
endif()

Version-Release number of selected component (if applicable):
cmake3-3.17.5-1.el7

Additional info:
Rust upstream CI uses a centos:7 container as the minimum supported linux-gnu environment for i686 and x86_64 builds, and that includes building new versions of LLVM. That currently uses cmake3 from EPEL, but we'll have to build our own cmake if the version isn't updated to meet LLVM's requirement.

FWIW, RHEL8 and RHEL9 both have cmake-3.20.2, even in the UBI repos. Fedora 36 and later all have cmake-3.25.2, recently updated on all branches.