Add gcc-toolset-12-gcc-c++ dependency to clang-libs

Resolves: rhbz#2061058

clang.spec

@@ -172,7 +172,7 @@ libomp-devel to enable -fopenmp.
 %package libs
 Summary: Runtime library for clang
 Requires: %{name}-resource-filesystem%{?_isa} = %{version}
-#Requires: gcc-toolset-11-gcc-c++
+Requires: gcc-toolset-12-gcc-c++
 Recommends: compiler-rt%{?_isa} = %{version}
 # libomp-devel is required, so clang can find the omp.h header when compiling
 # with -fopenmp.
@@ -402,7 +402,8 @@ mv ../clang-%{compat_ver}.src ../clang
 %ifarch %{arm}
 	-DCLANG_DEFAULT_LINKER=lld \
 %endif
-	-DCLANG_DEFAULT_UNWINDLIB=libgcc
+	-DCLANG_DEFAULT_UNWINDLIB=libgcc \
+	-DGCC_INSTALL_PREFIX=/opt/rh/gcc-toolset-12/root/usr
 
 %cmake_build