www/davix: fix build with clang 19
Clang 19 has become more strict about assigning to const class members,
resulting in errors similar to:
/wrkdirs/usr/ports/www/davix/work/davix-R_0_8_7/src/libs/rapidjson/document.h:319:82: error: cannot assign to non-static data member 'length' with const-qualified type 'const SizeType' (aka 'const unsigned int')
319 | GenericStringRef& operator=(const GenericStringRef& rhs) { s = rhs.s; length = rhs.length; }
| ~~~~~~ ^
/wrkdirs/usr/ports/www/davix/work/davix-R_0_8_7/src/libs/rapidjson/document.h:325:20: note: non-static data member 'length' declared const here
325 | const SizeType length; //!< length of the string (excluding the trailing NULL terminator)
| ~~~~~~~~~~~~~~~^~~~~~Upstream rapidjson has fixed this in commit 3b2441b8 [1], which simply
removes the assignment operator.
[1] https://github.com/Tencent/rapidjson/commit/3b2441b8
PR: 282515
Approved by: yuri (maintainer)
MFH: 2024Q4
(cherry picked from commit c3ec17f889effeee0a46d666dbd4f82c8cc77fac)