Determining if the function smtp_create_session exists in the esmtp failed with the following output:
Change Dir: /tmp/instance-0/output-1/build/log4cxx-0.12.0/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/make cmTC_e9ee9/fast && make[1]: Entering directory '/tmp/instance-0/output-1/build/log4cxx-0.12.0/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_e9ee9.dir/build.make CMakeFiles/cmTC_e9ee9.dir/build
make[2]: Entering directory '/tmp/instance-0/output-1/build/log4cxx-0.12.0/CMakeFiles/CMakeTmp'
Building CXX object CMakeFiles/cmTC_e9ee9.dir/CheckFunctionExists.cxx.o
/tmp/instance-0/output-1/host/bin/arm-buildroot-linux-gnueabihf-g++ --sysroot=/tmp/instance-0/output-1/host/arm-buildroot-linux-gnueabihf/sysroot    -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g0 -D_FORTIFY_SOURCE=1 -DCHECK_FUNCTION_EXISTS=smtp_create_session  -DNDEBUG   -std=c++17 -o CMakeFiles/cmTC_e9ee9.dir/CheckFunctionExists.cxx.o -c /tmp/instance-0/output-1/build/log4cxx-0.12.0/CMakeFiles/CheckLibraryExists/CheckFunctionExists.cxx
Linking CXX executable cmTC_e9ee9
/usr/bin/cmake -E cmake_link_script CMakeFiles/cmTC_e9ee9.dir/link.txt --verbose=1
/tmp/instance-0/output-1/host/bin/arm-buildroot-linux-gnueabihf-g++ --sysroot=/tmp/instance-0/output-1/host/arm-buildroot-linux-gnueabihf/sysroot  -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g0 -D_FORTIFY_SOURCE=1 -DCHECK_FUNCTION_EXISTS=smtp_create_session  -DNDEBUG    CMakeFiles/cmTC_e9ee9.dir/CheckFunctionExists.cxx.o  -o cmTC_e9ee9  -lesmtp 
/tmp/instance-0/output-1/host/lib/gcc/arm-buildroot-linux-gnueabihf/11.2.0/../../../../arm-buildroot-linux-gnueabihf/bin/ld: cannot find -lesmtp
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/cmTC_e9ee9.dir/build.make:87: cmTC_e9ee9] Error 1
make[2]: Leaving directory '/tmp/instance-0/output-1/build/log4cxx-0.12.0/CMakeFiles/CMakeTmp'
make[1]: *** [Makefile:121: cmTC_e9ee9/fast] Error 2
make[1]: Leaving directory '/tmp/instance-0/output-1/build/log4cxx-0.12.0/CMakeFiles/CMakeTmp'