Determining if the function pthread_create exists in the pthreads failed with the following output:
Change Dir: /home/buildroot/autobuild/instance-2/output-1/build/hackrf-2018.01.1/host/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/make cmTC_e579e/fast && make[1]: Entering directory '/home/buildroot/autobuild/instance-2/output-1/build/hackrf-2018.01.1/host/CMakeFiles/CMakeTmp'
/usr/bin/make  -f CMakeFiles/cmTC_e579e.dir/build.make CMakeFiles/cmTC_e579e.dir/build
make[2]: Entering directory '/home/buildroot/autobuild/instance-2/output-1/build/hackrf-2018.01.1/host/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_e579e.dir/CheckFunctionExists.c.o
/home/buildroot/autobuild/instance-2/output-1/host/bin/sparc-linux-gcc --sysroot=/home/buildroot/autobuild/instance-2/output-1/host/sparc-buildroot-linux-uclibc/sysroot   -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g0 -std=gnu90 -DCHECK_FUNCTION_EXISTS=pthread_create  -DNDEBUG   -o CMakeFiles/cmTC_e579e.dir/CheckFunctionExists.c.o   -c /home/buildroot/autobuild/instance-2/output-1/host/share/cmake-3.16/Modules/CheckFunctionExists.c
Linking C executable cmTC_e579e
/home/buildroot/autobuild/instance-2/output-1/host/bin/cmake -E cmake_link_script CMakeFiles/cmTC_e579e.dir/link.txt --verbose=1
/home/buildroot/autobuild/instance-2/output-1/host/bin/sparc-linux-gcc --sysroot=/home/buildroot/autobuild/instance-2/output-1/host/sparc-buildroot-linux-uclibc/sysroot -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os -g0 -std=gnu90 -DCHECK_FUNCTION_EXISTS=pthread_create  -DNDEBUG    CMakeFiles/cmTC_e579e.dir/CheckFunctionExists.c.o  -o cmTC_e579e  -lpthreads 
/home/buildroot/autobuild/instance-2/output-1/host/opt/ext-toolchain/bin/../lib/gcc/sparc-buildroot-linux-uclibc/10.3.0/../../../../sparc-buildroot-linux-uclibc/bin/ld: cannot find -lpthreads
collect2: error: ld returned 1 exit status
CMakeFiles/cmTC_e579e.dir/build.make:89: recipe for target 'cmTC_e579e' failed
make[2]: *** [cmTC_e579e] Error 1
make[2]: Leaving directory '/home/buildroot/autobuild/instance-2/output-1/build/hackrf-2018.01.1/host/CMakeFiles/CMakeTmp'
Makefile:124: recipe for target 'cmTC_e579e/fast' failed
make[1]: *** [cmTC_e579e/fast] Error 2
make[1]: Leaving directory '/home/buildroot/autobuild/instance-2/output-1/build/hackrf-2018.01.1/host/CMakeFiles/CMakeTmp'