[Bug libstdc++/86447] New: gcc 9.0 from r262456 can't build cross compiler for mingw-w64 target

[mateuszb at poczta dot onet.pl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86447

            Bug ID: 86447
           Summary: gcc 9.0 from r262456 can't build cross compiler for
                    mingw-w64 target
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mateuszb at poczta dot onet.pl
  Target Milestone: ---
            Target: mingw-w64

>From r262456 when I compile cross compiler (in Ubuntu) for mingw-w64 target
there is a bug:

libtool: compile:  /home/ma/m/build/bc_gcc/./gcc/xgcc -shared-libgcc
-B/home/ma/m/build/bc_gcc/./gcc -nostdinc++
-L/home/ma/m/build/bc_gcc/x86_64-w64-mingw32/libstdc++-v3/src
-L/home/ma/m/build/bc_gcc/x86_64-w64-mingw32/libstdc++-v3/src/.libs
-L/home/ma/m/build/bc_gcc/x86_64-w64-mingw32/libstdc++-v3/libsupc++/.libs
-L/home/ma/m/cross/x86_64-w64-mingw32/lib -L/home/ma/m/cross/mingw/lib -isystem
/home/ma/m/cross/x86_64-w64-mingw32/include -isystem
/home/ma/m/cross/mingw/include -B/home/ma/m/cross/x86_64-w64-mingw32/bin/
-B/home/ma/m/cross/x86_64-w64-mingw32/lib/ -isystem
/home/ma/m/cross/x86_64-w64-mingw32/include -isystem
/home/ma/m/cross/x86_64-w64-mingw32/sys-include
-I/home/ma/m/source/gcc-9/libstdc++-v3/../libgcc
-I/home/ma/m/build/bc_gcc/x86_64-w64-mingw32/libstdc++-v3/include/x86_64-w64-mingw32
-I/home/ma/m/build/bc_gcc/x86_64-w64-mingw32/libstdc++-v3/include
-I/home/ma/m/source/gcc-9/libstdc++-v3/libsupc++ -std=gnu++11
-fno-implicit-templates -Wall -Wextra -Wwrite-strings -Wcast-qual -Wabi
-fdiagnostics-show-location=once -ffunction-sections -fdata-sections
-frandom-seed=cow-stdexcept.lo -g -O2 -c
/home/ma/m/source/gcc-9/libstdc++-v3/src/c++11/cow-stdexcept.cc -o
cow-stdexcept.o
cc1plus: warning: -Wabi won't warn about anything [-Wabi]
cc1plus: note: -Wabi warns about differences from the most up-to-date ABI,
which is also used by default
cc1plus: note: use e.g. -Wabi=11 to warn about changes from GCC 7
/home/ma/m/source/gcc-9/libstdc++-v3/src/c++11/cow-stdexcept.cc:67:3: error:
function 'std::logic_error::logic_error(std::logic_error&&)' defaulted on its
redeclaration with an exception-specification that differs from the implicit
exception-specification ''
   logic_error::logic_error(logic_error&& e) noexcept = default;
   ^~~~~~~~~~~
/home/ma/m/source/gcc-9/libstdc++-v3/src/c++11/cow-stdexcept.cc:79:3: error:
function 'std::runtime_error::runtime_error(std::runtime_error&&)' defaulted on
its redeclaration with an exception-specification that differs from the
implicit exception-specification ''
   runtime_error::runtime_error(runtime_error&& e) noexcept = default;
   ^~~~~~~~~~~~~
Makefile:562: recipe for target 'cow-stdexcept.lo' failed
make[5]: *** [cow-stdexcept.lo] Error 1

The bug is in phase when new compiled gcc is trying to compile libraries.