This is caused by 2efb237ffc68ec9bb17982434f5941bfa14f8b50, which has references to `strchrnul`, 
which does not exist on i686w-64-mingw32:

   ```
   g++ -std=c++11  -fno-PIE -c  -DIN_GCC_FRONTEND -g -D__USE_MINGW_ACCESS -DIN_GCC 
-fno-exceptions -fno-rtti -fasynchronous-unwind-tables -W -Wall -Wno-narrowing -Wwrite-strings 
-Wcast-qual -Wno-format -Wmissing-format-attribute -Woverloaded-virtual -pedantic -Wno-long-long 
-Wno-variadic-macros -Wno-overlength-strings   -DHAVE_CONFIG_H -I. -Icp -I../../gcc/gcc 
-I../../gcc/gcc/cp -I../../gcc/gcc/../include -I../../gcc/gcc/../libcpp/include 
-I../../gcc/gcc/../libcody -I/mingw32/include -I/mingw32/include -I/mingw32/include 
-I../../gcc/gcc/../libdecnumber -I../../gcc/gcc/../libdecnumber/bid -I../libdecnumber 
-I../../gcc/gcc/../libbacktrace -I/mingw32/include -D__USE_MINGW_ANSI_STDIO=1 -I/mingw32/include -o 
cp/error.o -MT cp/error.o -MMD -MP -MF cp/.deps/error.TPo ../../gcc/gcc/cp/error.cc
   ../../gcc/gcc/cp/contracts.cc: In function 'bool role_name_equal(const char*, const char*)':
   ../../gcc/gcc/cp/contracts.cc:213:21: error: 'strchrnul' was not declared in this scope; did you 
mean 'strchr'?
     213 |   size_t role_len = strchrnul (role, ':') - role;
         |                     ^~~~~~~~~
         |                     strchr
   make[3]: *** [Makefile:1146: cp/contracts.o] Error 1
   make[3]: *** Waiting for unfinished jobs....
   ```


Proposed solution:

   ```
   size_t role_len = strcspn (role, ":");
   ```



-- 
Best regards,
LIU Hao