clang-scan-deps is used to generate dependency information from C++20 modules according to proposed standard ISO/IEC WG21 P1689R5[0]. It is required by common build tools (e.g., CMake) to build C++ sources that use modules. Since this is a core build tool, install it by default, not gated behind MK_CLANG_EXTRAS. [0] https://www.open-std.org/JTC1/SC22/WG21/docs/papers/2022/p1689r5.html MFC after: 3 days Reviewed by: kevans, dim Approved by: kevans (mentor) Requested by: jbo Differential Revision: https://reviews.freebsd.org/D51044 (cherry picked from commit d3c06bed2c16b434dd49958dee5de8c55ad00b85)