devel/build2: fix build with libc++ >= 20
With libc++ 20 or higher devel/build2 fails to build, with errors
similar to:
In file included from libbuild2/utility.cxx:27:
./libbuild2/script/regex.hxx:620:10: error: 'make_unsigned' cannot be specialized: Users are not allowed to specialize this standard library entity [-Winvalid-specialization]
620 | struct make_unsigned<build2::script::regex::line_char>
| ^
/usr/include/c++/v1/__type_traits/make_unsigned.h:75:8: note: marked '_Clang::no_specializations' here
75 | struct _LIBCPP_NO_SPECIALIZATIONS make_unsigned {
| ^
/usr/include/c++/v1/__config:1167:9: note: expanded from macro '_LIBCPP_NO_SPECIALIZATIONS'Upstream committed a fix for this in
https://github.com/build2/build2/commit/7cf9cec, so add that as a patch
file.
PR: 292867
Approved by: fuz (maintainer)
MFH: 2026Q1
(cherry picked from commit ca0ca0a01359fe5acccf5a21c4acd2ceceefbd7a)