Add missing #if for clang #3176

Job	Run time
ubuntu-clang-deprecated Debug	27m 29s
ubuntu-clang-deprecated Release	24m 14s
ubuntu-clang-quaternions Debug	23m 45s
ubuntu-clang-quaternions Release	23m 8s
ubuntu-clang-tbb Debug	22m 59s
ubuntu-clang-tbb Release	24m 43s
ubuntu-clang-cayleymap Debug	21m 59s
ubuntu-clang-cayleymap Release	30m 1s
ubuntu-clang-system-libs Debug	21m 19s
ubuntu-clang-system-libs Release	23m 18s
ubuntu-no-boost Debug	22m 0s
ubuntu-no-boost Release	23m 25s
ubuntu-no-unstable Debug	17m 56s
ubuntu-no-unstable Release	19m 0s
	5h 25m 16s

Provide feedback