[science-kit] sci-mathematics/z3-4.15.8 doesn't compile

```
FAILED: [code=1] src/ast/CMakeFiles/ast.dir/array_decl_plugin.cpp.o
/usr/bin/x86_64-pc-linux-gnu-g++ -D_EXTERNAL_RELEASE -D_MP_INTERNAL -I/var/tmp/portage/sci-mathematics/z3-4.15.8/work/z3-4.15.8_build/src -I/var/tmp/portage/sci-mathematics/z3-4.15.8/work/z3-4.15.8/src -mtune=generic -O2 -pipe -Werror=odr -Werror=return-type -std=gnu++20 -fPIC -fvisibility=hidden -fvisibility-inlines-hidden -mfpmath=sse -msse -msse2 -Wall -MD -MT src/ast/CMakeFiles/ast.dir/array_decl_plugin.cpp.o -MF src/ast/CMakeFiles/ast.dir/array_decl_plugin.cpp.o.d -o src/ast/CMakeFiles/ast.dir/array_decl_plugin.cpp.o -c /var/tmp/portage/sci-mathematics/z3-4.15.8/work/z3-4.15.8/src/ast/array_decl_plugin.cpp
/var/tmp/portage/sci-mathematics/z3-4.15.8/work/z3-4.15.8/src/ast/array_decl_plugin.cpp:20:9: fatal error: format: No such file or directory
20 | #include
| ^~~~~~~~
compilation terminated.
```
It seems that we need >=GCC-13 and C++20.

Start with the reported CMake build command and the sci-mathematics/z3-4.15.8 package configuration, then verify the compiler and C++ standard requirements around the missing header. Done means the package compiles successfully with the supported GCC and C++20 configuration.

Written by the indexing model from the issue text.