Help: Add cmake-toolchains.7 manual

Create a manual for toolchain related docs.
Merge topic 'cmake-toolchains-manual' into next

c45b5ce Help: Add cmake-toolchains.7 manual
Merge topic 'cmake-toolchains-manual'

c45b5ce Help: Add cmake-toolchains.7 manual
3e3f8b4 Help: Document the CMAKE_FIND_ROOT_PATH* variables.
531c108 Help: Document the CMAKE_TOOLCHAIN_FILE.
Merge branch 'master' into next
Merge topic 'filter-showincludes-in-launcher'

e5e3f3d CTest: filter /showIncludes output from ninja compile launcher
Merge branch 'master' into next