gnu: clang-runtime-18: Build with gcc-13.
Avoid
In file included from /tmp/guix-build-clang-runtime-18.1.8.drv-0/source/build/lib/fuzzer/libcxx_fuzzer_x86_64/include/c++/v1/__exception/nested_exception.h:18,
from /tmp/guix-build-clang-runtime-18.1.8.drv-0/source/build/lib/fuzzer/libcxx_fuzzer_x86_64/include/c++/v1/exception:83,
from /tmp/guix-build-clang-runtime-18.1.8.drv-0/source/libcxxabi/src/cxa_aux_runtime.cpp:13:
/tmp/guix-build-clang-runtime-18.1.8.drv-0/source/build/lib/fuzzer/libcxx_fuzzer_x86_64/include/c++/v1/__type_traits/is_convertible.h:28:77: error: there are no arguments to ‘__is_convertible’ that depend on a template parameter, so a declaration of ‘__is_convertible’ must be available [-fpermissive]
28 | struct _LIBCPP_TEMPLATE_VIS is_convertible : public integral_constant<bool, __is_convertible(_T1, _T2)> {};
by using gcc-13.
* gnu/packages/llvm.scm (clang-runtime-from-llvm)[native-inputs]: Use gcc-13
for version 18.
Change-Id: Ib01403665af7a8014e6da612bc6f31257e498d88