/usr/include/clc/geometric/dot.inc is in libclc-dev 0~git20140101-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1
_CLC_OVERLOAD _CLC_DECL __CLC_FLOAT dot(__CLC_FLOATN p0, __CLC_FLOATN p1);