today I did an upgrade but the package clang9-9.0.1-10.3 failed to install with
many errors like:

File /usr/bin/clang
  from install of
     clang9-9.0.1-10.3.x86_64 (openSUSE-20190726-0)
  conflicts with file from package
     clang10-10.0.0-1.2.x86_64 (@System)

File /usr/bin/clang
  from install of
     clang9-9.0.1-10.3.x86_64 (openSUSE-20190726-0)
  conflicts with file from package
     clang8-8.0.1-8.3.x86_64 (@System)

Because I didn't have problems with the last upgrade to clang9-9.0.1-10.1, I
checked if there where any difference in the spec file for llvm9-9.0.1-10.1 and
llvm9-9.0.1-10.3.
The spec files are essentially the same, therefore the issue has to be related
to some change introduced in the build system.

The output of:
  rpm -qlpv clang9-9.0.1-10.1.x86_64.rpm | grep '/usr/bin/clang '
is:
lrwxrwxrwx    1 root     root                       23 Apr  9 21:10
/usr/bin/clang -> /etc/alternatives/clang

and the output of:
  rpm -qlpv clang9-9.0.1-10.3.x86_64.rpm | grep '/usr/bin/clang '
is:
lrwxrwxrwx    1 root     root                       28 May 11 12:11
/usr/bin/clang -> ../../etc/alternatives/clang

As you can see the build system was creating /usr/bin/clang as a link to 
/etc/alternatives/clang before, but now the link point to
../../etc/alternatives/clang.
This difference is causing the update failure.