Include <boost/config.h> in the has_backtrace.cpp detector

[gysevvlad]

Hello!

I ran into an issue where has_backtrace.cpp does not include <boost/config.hpp> and therefore doesn’t pick up user.hpp with the required defines such as BOOST_STACKTRACE_BACKTRACE_INCLUDE_FILE.

Would it be possible to include the following patch, similar to how it’s done in has_addr2line.cpp?

diff --unified --recursive boost-1.83.0.orig/libs/stacktrace/build/has_backtrace.cpp boost-1.83.0/libs/stacktrace/build/has_backtrace.cpp
--- boost-1.83.0.orig/libs/stacktrace/build/has_backtrace.cpp   2026-04-27 21:08:22.774083629 +0200
+++ boost-1.83.0/libs/stacktrace/build/has_backtrace.cpp        2026-04-27 21:10:06.994861653 +0200
@@ -4,6 +4,8 @@
 // accompanying file LICENSE_1_0.txt or copy at
 // http://www.boost.org/LICENSE_1_0.txt)
 
+#include <boost/config.hpp>
+
 #ifdef BOOST_STACKTRACE_BACKTRACE_INCLUDE_FILE
 #   include BOOST_STACKTRACE_BACKTRACE_INCLUDE_FILE
 #else

I’m not very familiar with b2/Jam, so I’m not sure whether it’s appropriate to include <boost/config.hpp> in feature detection sources, or whether this macro is intended to be defined in user.hpp in the first place.