Workaround for b2 not supporting clang 3.6 #87

Job	Run time
windows-images (build-msvc14_1, cppalliance/dronevs2017:1)	2s
linux-images (build-clang3_6, build-clang3_6, linux/amd64)	5s
windows-images (build-msvc14_2, cppalliance/dronevs2019:1)	7s
linux-images (build-clang7, build-clang7, linux/amd64)	3s
linux-images (build-clang11, build-clang11, linux/amd64)	8s
linux-images (build-clang14, build-clang14, linux/amd64, linux/arm64/v8)	5s
windows-images (build-msvc14_3, cppalliance/dronevs2022:1)	7s
linux-images (build-clang16, build-clang16, linux/amd64)	6s
linux-images (build-clang16-i386, build-clang16-i386, linux/amd64)	6s
linux-images (build-gcc5, build-gcc5, linux/amd64)	8s
linux-images (build-gcc6, build-gcc6, linux/amd64)	3s
linux-images (build-gcc10, build-gcc10, linux/amd64)	5s
linux-images (build-gcc11, build-gcc11, linux/amd64, linux/arm64/v8)	4s
linux-images (build-gcc13, build-gcc13, linux/amd64)	4s
linux-images (build-cmake3_8, build-cmake3_8, linux/amd64)	7s
linux-images (build-noopenssl, build-noopenssl, linux/amd64)	5s
linux-images (build-docs, build-docs, linux/amd64)	6s
linux-images (mysql5, mysql5, linux/amd64)	5s
linux-images (mysql8, mysql8, linux/amd64, linux/arm64/v8)	5s
linux-images (mariadb, mariadb, linux/amd64, linux/arm64/v8)	4s
	1m 45s

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