try setup flag for clang3 #916

Job	Run time
Clean up previous branch jobs	7s
Package builder app	8s
Unit Tests	4s
Sanity Test (ubuntu-22.04)	1m 46s
Sanity Test (macos-11)	2m 59s
cross_compile (linux-armv6)	10m 11s
Sanity Test (macos-12)	3m 1s
compilers (clang-9)	51s
cross_compile (linux-armv7)	10m 17s
downstream (aws-c-mqtt)	11m 15s
Sanity Test (windows-2022)	3m 11s
compilers (clang-10)	38s
cross_compile (linux-armv8)	9m 52s
downstream (aws-c-http)	4m 3s
compilers (clang-11)	28s
downstream (aws-crt-python)	6m 30s
compilers (gcc-7)	34s
downstream (aws-crt-cpp)	6m 55s
release_notes (aws-crt-python)	36s
compilers (gcc-8)	35s
downstream (aws-crt-java)	7m 54s
aws-c-cal (manylinux1-x86)	2m 25s
release_notes (aws-iot-device-sdk-python-v2)	3s
compilers (gcc-9)	31s
downstream (aws-crt-nodejs)	5m 13s
aws-c-cal (manylinux1-x64)	2m 9s
compilers (gcc-10)	26s
aws-c-cal (manylinux2014-x86)	2m 45s
compilers (gcc-11)	1m 25s
swift (swift-5-ubuntu-x64)	38s
aws-c-cal (manylinux2014-x64)	2m 39s
swift (swift-5-centos-x64)	44s
aws-c-cal (manylinux2014-aarch64)	23m 19s
swift (swift-5-al2-x64)	43s
aws-c-cal (musllinux-1-1-aarch64)	25m 45s
aws-c-cal (musllinux-1-1-x64)	2m 37s
std-compat (gcc-8, c++11)	6m 36s
std-compat (gcc-8, c++14)	8m 22s
std-compat (gcc-8, c++17)	6m 29s
std-compat (gcc-8, c++2a)	6m 4s
std-compat (clang-9, c++11)	6m 14s
std-compat (clang-9, c++14)	5m 35s
std-compat (clang-9, c++17)	5m 57s
std-compat (clang-9, c++2a)	6m 22s
All Sanity Tests passed	1s
	3h 24m 57s

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