the exact version of GCC:
gcc-9.1.0

the system type:
NetgearReadyNAS Duo (http://wiki.dietpc.org/index.php/DIET-PC_on_SPARC_ReadyNAS)

the options given when GCC was configured/built:
../gcc-9.1.0/configure CC=/opt/gcc-7.1/bin/gcc CXX=/opt/gcc-7.1/bin/g++ --enable-languages=c,c++,go --prefix=/opt/gcc-9.1 --with-cpu=v7 --with-mpc=/usr/local --with-mpfr=/usr/local --with-gmp=/usr/local --with-isl=/usr/local/ --disable-libstdcxx-pch --disable-linux-futex --disable-libsanitizer --enable-__cxa_atexit --enable-nls --enable-clocale=gnu --enable-debug --disable-doc --disable-libcilkrts --disable-libitm


the complete command line that triggers the bug;
/usr/local/bin/make

the compiler output (error messages, warnings, etc.);
[...]
make[2]: Entering directory '/c/backup/fes-readynasduo/gcc-9.1.0-compiled/gotools'
/backup/fes-readynasduo/gcc-9.1.0-compiled/./gcc/gccgo -B/backup/fes-readynasduo/gcc-9.1.0-compiled/./gcc/ -B/opt/gcc-9.1/sparc-unknown-linux-gnu/bin/ -B/opt/gcc-9.1/sparc-unknown-linux-gnu/lib/ -isystem /opt/gcc-9.1/sparc-unknown-linux-gnu/include -isystem /opt/gcc-9.1/sparc-unknown-linux-gnu/sys-include   -g -O2 -I ../sparc-unknown-linux-gnu/libgo -static-libstdc++ -static-libgcc  -L ../sparc-unknown-linux-gnu/libgo -L ../sparc-unknown-linux-gnu/libgo/.libs -o go ../../gcc-9.1.0/gotools/../libgo/go/cmd/go/alldocs.go ../../gcc-9.1.0/gotools/../libgo/go/cmd/go/go11.go ../../gcc-9.1.0/gotools/../libgo/go/cmd/go/main.go ../sparc-unknown-linux-gnu/libgo/libgotool.a
../sparc-unknown-linux-gnu/libgo/.libs/libgo.so: undefined reference to `fdopendir'
../sparc-unknown-linux-gnu/libgo/.libs/libgo.so: undefined reference to `__sync_bool_compare_and_swap_4'
../sparc-unknown-linux-gnu/libgo/.libs/libgo.so: undefined reference to `__tls_get_addr'
../sparc-unknown-linux-gnu/libgo/.libs/libgo.so: undefined reference to `__go_openat'
../sparc-unknown-linux-gnu/libgo/.libs/libgo.so: undefined reference to `fstatat64'
collect2: error: ld returned 1 exit status
make[2]: *** [Makefile:821: go] Error 1
make[2]: Leaving directory '/c/backup/fes-readynasduo/gcc-9.1.0-compiled/gotools'
make[1]: *** [Makefile:15520: all-gotools] Error 2
make[1]: Leaving directory '/c/backup/fes-readynasduo/gcc-9.1.0-compiled'
make: *** [Makefile:993: all] Error 2

 ldd -r /backup/fes-readynasduo/gcc-9.1.0-compiled/gcc/gccgo                                                                                                          libiconv.so.2 => /usr/local/lib/libiconv.so.2 (0x2002c000)                                                                                                                          libm.so.6 => /lib/libm.so.6 (0x20124000)                                                                                                                                            libc.so.6 => /lib/libc.so.6 (0x201b8000)                                                                                                                                            /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x20000000)

/backup/fes-readynasduo/gcc-9.1.0-compiled/gcc/gccgo --version                                                                                                    gccgo (GCC) 9.1.0                                                                                                                                                                   Copyright (C) 2019 Free Software Foundation, Inc.                                                                                                                                   This is free software; see the source for copying conditions.  There is NO                                                                                                          warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 

Not sure which information is important for this bug.