Determining if the include file pthread.h exists failed with the following output:
Change Dir: /home/buildroot/autobuild/instance-1/output/build/optee-client-3.4.0/CMakeFiles/CMakeTmp

Run Build Command:"/usr/bin/make" "cmTC_8ed5e/fast"
make[1]: Entering directory '/home/buildroot/autobuild/instance-1/output/build/optee-client-3.4.0/CMakeFiles/CMakeTmp'
/usr/bin/make -f CMakeFiles/cmTC_8ed5e.dir/build.make CMakeFiles/cmTC_8ed5e.dir/build
make[2]: Entering directory '/home/buildroot/autobuild/instance-1/output/build/optee-client-3.4.0/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_8ed5e.dir/CheckIncludeFile.c.o
/home/buildroot/autobuild/instance-1/output/host/bin/arm-linux-gcc --sysroot=/home/buildroot/autobuild/instance-1/output/host/arm-buildroot-linux-uclibcgnueabihf/sysroot   -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os   -DNDEBUG   -o CMakeFiles/cmTC_8ed5e.dir/CheckIncludeFile.c.o   -c /home/buildroot/autobuild/instance-1/output/build/optee-client-3.4.0/CMakeFiles/CMakeTmp/CheckIncludeFile.c
/home/buildroot/autobuild/instance-1/output/build/optee-client-3.4.0/CMakeFiles/CMakeTmp/CheckIncludeFile.c:1:21: fatal error: pthread.h: No such file or directory
 #include <pthread.h>
                     ^
compilation terminated.
CMakeFiles/cmTC_8ed5e.dir/build.make:65: recipe for target 'CMakeFiles/cmTC_8ed5e.dir/CheckIncludeFile.c.o' failed
make[2]: *** [CMakeFiles/cmTC_8ed5e.dir/CheckIncludeFile.c.o] Error 1
make[2]: Leaving directory '/home/buildroot/autobuild/instance-1/output/build/optee-client-3.4.0/CMakeFiles/CMakeTmp'
Makefile:126: recipe for target 'cmTC_8ed5e/fast' failed
make[1]: *** [cmTC_8ed5e/fast] Error 2
make[1]: Leaving directory '/home/buildroot/autobuild/instance-1/output/build/optee-client-3.4.0/CMakeFiles/CMakeTmp'