Determining if the function dlopen exists in the dl failed with the following output:
Change Dir: /data/buildroot-test/instance-0/output-1/build/libuhttpd-3.4.0/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/make cmTC_2aff4/fast && make[1]: Entering directory '/data/buildroot-test/instance-0/output-1/build/libuhttpd-3.4.0/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_2aff4.dir/build.make CMakeFiles/cmTC_2aff4.dir/build
make[2]: Entering directory '/data/buildroot-test/instance-0/output-1/build/libuhttpd-3.4.0/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_2aff4.dir/CheckFunctionExists.c.o
/data/buildroot-test/instance-0/output-1/host/bin/arm-linux-gcc --sysroot=/data/buildroot-test/instance-0/output-1/host/arm-buildroot-linux-uclibcgnueabi/sysroot   -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -static -DCHECK_FUNCTION_EXISTS=dlopen  -DNDEBUG   -o CMakeFiles/cmTC_2aff4.dir/CheckFunctionExists.c.o   -c /data/buildroot-test/instance-0/output-1/host/share/cmake-3.15/Modules/CheckFunctionExists.c
Linking C executable cmTC_2aff4
/data/buildroot-test/instance-0/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_2aff4.dir/link.txt --verbose=1
/data/buildroot-test/instance-0/output-1/host/bin/arm-linux-gcc --sysroot=/data/buildroot-test/instance-0/output-1/host/arm-buildroot-linux-uclibcgnueabi/sysroot -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -static -DCHECK_FUNCTION_EXISTS=dlopen  -DNDEBUG  -static  CMakeFiles/cmTC_2aff4.dir/CheckFunctionExists.c.o  -o cmTC_2aff4 -ldl 
/data/buildroot-test/instance-0/output-1/host/opt/ext-toolchain/bin/../lib/gcc/arm-buildroot-linux-uclibcgnueabi/8.3.0/../../../../arm-buildroot-linux-uclibcgnueabi/bin/ld: CMakeFiles/cmTC_2aff4.dir/CheckFunctionExists.c.o: in function `main':
CheckFunctionExists.c:(.text.startup+0xc): undefined reference to `dlopen'
collect2: error: ld returned 1 exit status
make[2]: *** [CMakeFiles/cmTC_2aff4.dir/build.make:87: cmTC_2aff4] Error 1
make[2]: Leaving directory '/data/buildroot-test/instance-0/output-1/build/libuhttpd-3.4.0/CMakeFiles/CMakeTmp'
make[1]: *** [Makefile:121: cmTC_2aff4/fast] Error 2
make[1]: Leaving directory '/data/buildroot-test/instance-0/output-1/build/libuhttpd-3.4.0/CMakeFiles/CMakeTmp'