Update cmake_minimum_required to 3.9 #1136

Job	Run time
linux-shared-libs	11m 13s
clang-sanitizers (,thread)	11m 56s
linux-compiler-compat (clang-3)	11m 21s
clang-sanitizers (,address,undefined)	11m 51s
linux-compat (manylinux1-x64)	10m 51s
linux-compat (manylinux1-x86)	10m 46s
linux-compiler-compat (clang-6)	12m 0s
windows	11m 42s
linux-compat (manylinux2014-x64)	11m 13s
windows-shared-libs	12m 22s
linux-compat (manylinux2014-x86)	10m 49s
linux-compiler-compat (clang-8)	12m 17s
linux-compat (al2-x64)	10m 39s
windows-vc14 (x86)	10m 47s
linux-compiler-compat (clang-9)	12m 13s
linux-compat (fedora-34-x64)	10m 55s
linux-compiler-compat (clang-10)	11m 43s
windows-vc14 (x64)	14m 16s
linux-compat (opensuse-leap)	11m 41s
linux-compiler-compat (clang-11)	11m 53s
linux-compat (rhel8-x64)	11m 2s
linux-compiler-compat (gcc-4.8)	11m 1s
linux-compiler-compat (gcc-5)	11m 29s
linux-compiler-compat (gcc-6)	11m 18s
macos	10m 20s
linux-compiler-compat (gcc-7)	11m 8s
linux-compiler-compat (gcc-8)	11m 50s
macos-x64	10m 58s
windows-app-verifier	14m 25s
downstream	11m 43s
	5h 47m 42s

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