gcc 15.0.2+mingw 13.0.0 libstdc++-v3 build error

I'm trying to build mingw 13.0.0 with gcc 15.0.2 toolchain on Windows using another mingw 13.0.0 with gcc 15.0.2 build under busybox shell. As described in this tutorial, I first configured, built and installed GNU binutils 2.45.1 with following commands:

../path/to/binutils-configure --prefix=<my-prefix> --with-sysroot=<same-as-prefix> --enable-year2038 --host=x86_64-w64-mingw32 --target=x86_64-w64-mingw32 --enable-stage1-checking=all make && make install

Then, I install mingw32 header set:

../path/to/mingw-headers-configure --prefix=<my-prefix>/x86_64-w64-mingw32 --with-default-msvcrt=msvcrt --enable-sdk=none --host=x86_64-w64-mingw32 make && make install

After all that, I create needed folders and install raw gcc compiler:

../path/to/gcc-configure --prefix=<my-prefix> --with-sysroot=<same-as-prefix> --host=x86_64-w64-mingw32 --target=x86_64-w64-mingw32 --enable-64bit --enable-year2038 --enable-version-specific-runtime-libs --enable-static --disable-shared --with-dwarf --enable-libgomp --enable-libssp --disable-multilib --enable-__cxa_atexit --enable-threads=posix --enable-mingw-wildcard --disable-win32-registry --enable-fast-install=no --enable-ld=yes --enable-plugin --enable-stage1-checking=all make all-gcc && make install-gcc

At the end I build mingw-crt and rest part of gcc:

../path/to/mingw-crt-configure --prefix=<my-prefix> --enable-lib64 --disable-lib32 --host=x86_64-w64-mingw32 --with-default-msvcrt=msvcrt make && make install cd to-gcc-build-folder make

The problem occurs when I try to build rest of gcc: when building libstdc++-v3 compiler gives me error that numerous options are valid for some language (it prints whitespace as it's name) but not for C++:

cc1plus.exe: warning: "-Werror=" argument "-nostdinc++" is not valid for C++ cc1plus.exe: warning: "-Werror=" argument "-std=gnu++98" is not valid for C++ cc1plus.exe: warning: "-Werror=" argument "-fno-implicit-templates" is not valid for C++ // and also some warnings from preprocessor: warning: option '-Wc++11-extensions' is valid for but not for C++ [-Wpragmas] 40 | #pragma GCC diagnostic ignored "-Wc++11-extensions" // ..and a lot more of these...

and then it fails to build because throw(...) exception specifier was removed in c++17 (I must build for gnu c++98 standart).
I tried to search some web, but apparently nobody else have ever encountered such problem. What may be cause to this and how I can fix it?
I try to build MinGW with GCC on Windows 10 with x86_64 CPU.