Cross compile failure on v1.34.0 with success on v1.33.0

[j-c-cook]

Describe the bug

-- Found assembler: buildroot/tmp/toolchain/bin/arm-linux-gnueabihf-gcc
Copying platform assembly files from /home/jackcook/Documents/sdk-workspace/aws-iot-device-sdk-cpp-v2/crt/aws-crt-cpp/crt/aws-lc/generated-src/linux-x86/crypto/ to /home/jackcook/Documents/sdk-workspace/aws-iot-device-sdk-cpp-v2/build/deps/AWSLC/crypto
-- Looking for pthread.h
-- Looking for pthread.h - not found
CMake Error at /usr/share/cmake-3.16/Modules/FindPackageHandleStandardArgs.cmake:146 (message):
  Could NOT find Threads (missing: Threads_FOUND)
Call Stack (most recent call first):
  /usr/share/cmake-3.16/Modules/FindPackageHandleStandardArgs.cmake:393 (_FPHSA_FAILURE_MESSAGE)
  /usr/share/cmake-3.16/Modules/FindThreads.cmake:220 (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
  crypto/CMakeLists.txt:705 (find_package)


-- Configuring incomplete, errors occurred!
See also "/home/jackcook/Documents/sdk-workspace/aws-iot-device-sdk-cpp-v2/build/deps/AWSLC/CMakeFiles/CMakeOutput.log".
See also "/home/jackcook/Documents/sdk-workspace/aws-iot-device-sdk-cpp-v2/build/deps/AWSLC/CMakeFiles/CMakeError.log".
CMake Error at crt/aws-crt-cpp/crt/aws-c-common/cmake/AwsPrebuildDependency.cmake:52 (message):
  Configuration failed for dependency project AWSLC
Call Stack (most recent call first):
  crt/aws-crt-cpp/CMakeLists.txt:107 (aws_prebuild_dependency)


-- Configuring incomplete, errors occurred!

Expected Behavior

A successful build, make and make install like I can get with v1.33.

Current Behavior

Claims that threads are missing, so it seems that CMAKE_SYSROOT is not being propagated to the location that cannot locate Threads.

Reproduction Steps

cmake -DCMAKE_INSTALL_PREFIX=/home/jackcook/aws-iot-cpp-sdk \
-DCMAKE_BUILD_TYPE="Debug" \
-DCMAKE_C_COMPILER=buildroot/tmp/toolchain/bin/arm-linux-gnueabihf-gcc \
-DCMAKE_CXX_COMPILER=buildroot/tmp/toolchain/bin/arm-linux-gnueabihf-g++ \
-DCMAKE_SYSTEM_NAME=Linux \
-DCMAKE_SYSTEM_PROCESSOR=arm \
-DCMAKE_SYSROOT=buildroot/libs/br_pjt/output/staging/arm-buildroot-linux-gnueabihf/sysroot \
-DCMAKE_FIND_ROOT_PATH=buildroot/libs/br_pjt/output/staging/arm-buildroot-linux-gnueabihf/sysroot \
..

Possible Solution

There seems to be an issue in CMakeLists in v1.34 that wasn't present in v1.33.

Additional Information/Context

No response

SDK version used

v1.34.0

Environment details (OS name and version, etc.)

arm-linux-gnueabihf 7.0.5 2019.12

[sfod]

This failure is for prebuilding one of the dependencies, aws-lc. CMake configuration logs should contain cmake command that was used to prebuild aws-lc, something similar to the following:

$ cmake -S aws-iot-device-sdk-cpp-v2 -B build
-- AWS SDK C++ 1.34.0-dev+f661d209
...

-- cmake command for dependency AWSLC: /usr/bin/cmake3;-DCMAKE_CXX_COMPILER=...     // <=== this line

Can you provide this command here?