Start to require clang's major version on builds

In recent daily snapshot builds, libomp started to build with older
clang versions that are not binary compatible with the latest libomp,
causing build issues.

Requiring a clang version that is identical to libomp may prevent these
errors and will also help in avoiding disabling features unintentionally.

libomp.spec

@@ -18,7 +18,7 @@
 
 Name: libomp
 Version: %{libomp_version}%{?rc_ver:~rc%{rc_ver}}
-Release: 3%{?dist}
+Release: 4%{?dist}
 Summary: OpenMP runtime for clang
 
 License: Apache-2.0 WITH LLVM-exception OR NCSA
@@ -27,7 +27,7 @@ Source0: https://github.com/llvm/llvm-project/releases/download/llvmorg-%{libomp
 Source1: https://github.com/llvm/llvm-project/releases/download/llvmorg-%{libomp_version}%{?rc_ver:-rc%{rc_ver}}/%{libomp_srcdir}.tar.xz.sig
 Source2: release-keys.asc
 
-BuildRequires: clang
+BuildRequires: clang >= %{maj_ver}
 # For clang-offload-packager
 BuildRequires: clang-tools-extra
 BuildRequires: cmake
@@ -133,6 +133,9 @@ rm -rf %{buildroot}%{_libdir}/libarcher_static.a
 %endif
 
 %changelog
+* Wed Jun 28 2023 Tulio Magno Quites Machado Filho <tuliom@redhat.com> - 16.0.5-4
+- Specify the required clang version at build time
+
 * Sat Jun 17 2023 Tom Stellard <tstellar@redhat.com> - 16.0.5-3
 - Remove libomp-test package