updating PGDG 12 devel on centos7 requires llvm5.0

Hi

I'm clearly missing something obvious but it's passed me by what that
might be, so a pointer would be appreciated...

Tried running yum update on my centos7 box. Get the following:

Error: Package: postgresql12-devel-12.5-1PGDG.rhel7.x86_64 (postgresql_12)
Requires: llvm5.0-devel >= 5.0

SCLO is enabled and it happily installs llvm7-toolset (and its various
subs) from there. But yum install llvm5.0-devel simply returns "No
package llvm5.0-devel available"

There's suggestions in the mailing list archives that actually this is
resolved by installing llvm7-devel package but it's not.

# yum list installed | grep llvm
llvm-toolset-7-clang.x86_64 5.0.1-4.el7 @sclo
llvm-toolset-7-clang-libs.x86_64 5.0.1-4.el7 @sclo
llvm-toolset-7-compiler-rt.x86_64 5.0.1-2.el7 @sclo
llvm-toolset-7-libomp.x86_64 5.0.1-2.el7 @sclo
llvm-toolset-7-llvm.x86_64 5.0.1-8.el7 @sclo
llvm-toolset-7-llvm-devel.x86_64 5.0.1-8.el7 @sclo
llvm-toolset-7-llvm-libs.x86_64 5.0.1-8.el7 @sclo
llvm-toolset-7-runtime.x86_64 5.0.1-4.el7 @sclo
llvm-toolset-7.0.x86_64 7.0.1-2.el7 @sclo
llvm-toolset-7.0-clang.x86_64 7.0.1-1.el7 @sclo
llvm-toolset-7.0-clang-libs.x86_64 7.0.1-1.el7 @sclo
llvm-toolset-7.0-compiler-rt.x86_64 7.0.1-3.el7 @sclo
llvm-toolset-7.0-libomp.x86_64 7.0.1-2.el7 @sclo
llvm-toolset-7.0-lld.x86_64 7.0.1-2.el7 @sclo
llvm-toolset-7.0-lld-libs.x86_64 7.0.1-2.el7 @sclo
llvm-toolset-7.0-lldb.x86_64 7.0.1-1.el7 @sclo
llvm-toolset-7.0-llvm.x86_64 7.0.1-4.el7 @sclo
llvm-toolset-7.0-llvm-devel.x86_64 7.0.1-4.el7 @sclo
llvm-toolset-7.0-llvm-libs.x86_64 7.0.1-4.el7 @sclo
llvm-toolset-7.0-python2-lit.noarch 0.7.1-1.el7 @sclo
llvm-toolset-7.0-runtime.x86_64 7.0.1-2.el7 @sclo

I tried adding the EPEL repo just in case that was the issue but it
hasn't made any difference.

Thanks

Geoff