Determining if the getpassphrase exist failed with the following output:
Change Dir: /home/buildroot/autobuild/instance-3/output-1/build/znc-1.7.5/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_2b88c/fast"
make[1]: Entering directory '/home/buildroot/autobuild/instance-3/output-1/build/znc-1.7.5/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_2b88c.dir/build.make CMakeFiles/cmTC_2b88c.dir/build
make[2]: Entering directory '/home/buildroot/autobuild/instance-3/output-1/build/znc-1.7.5/CMakeFiles/CMakeTmp'
Building CXX object CMakeFiles/cmTC_2b88c.dir/CheckSymbolExists.cxx.o
/home/buildroot/autobuild/instance-3/output-1/host/bin/mips64el-linux-g++ --sysroot=/home/buildroot/autobuild/instance-3/output-1/host/mips64el-buildroot-linux-uclibc/sysroot    -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os   -DNDEBUG   -o CMakeFiles/cmTC_2b88c.dir/CheckSymbolExists.cxx.o -c /home/buildroot/autobuild/instance-3/output-1/build/znc-1.7.5/CMakeFiles/CMakeTmp/CheckSymbolExists.cxx
/home/buildroot/autobuild/instance-3/output-1/build/znc-1.7.5/CMakeFiles/CMakeTmp/CheckSymbolExists.cxx: In function 'int main(int, char**)':
/home/buildroot/autobuild/instance-3/output-1/build/znc-1.7.5/CMakeFiles/CMakeTmp/CheckSymbolExists.cxx:8:19: error: 'getpassphrase' was not declared in this scope
   return ((int*)(&getpassphrase))[argc];
                   ^
CMakeFiles/cmTC_2b88c.dir/build.make:65: recipe for target 'CMakeFiles/cmTC_2b88c.dir/CheckSymbolExists.cxx.o' failed
make[2]: *** [CMakeFiles/cmTC_2b88c.dir/CheckSymbolExists.cxx.o] Error 1
make[2]: Leaving directory '/home/buildroot/autobuild/instance-3/output-1/build/znc-1.7.5/CMakeFiles/CMakeTmp'
Makefile:126: recipe for target 'cmTC_2b88c/fast' failed
make[1]: *** [cmTC_2b88c/fast] Error 2
make[1]: Leaving directory '/home/buildroot/autobuild/instance-3/output-1/build/znc-1.7.5/CMakeFiles/CMakeTmp'

File /home/buildroot/autobuild/instance-3/output-1/build/znc-1.7.5/CMakeFiles/CMakeTmp/CheckSymbolExists.cxx:
/* */
#include <stdlib.h>

int main(int argc, char** argv)
{
  (void)argv;
#ifndef getpassphrase
  return ((int*)(&getpassphrase))[argc];
#else
  (void)argc;
  return 0;
#endif
}