At CPack running time the `CMAKE_PROJECT_HOMEPAGE_URL` variable
is not set.
Internal CPack modules (e.g. CPackDEB, CPackRPM, CPackFreeBSD)
should use `CPACK_PACKAGE_HOMEPAGE_URL` instead, which is available
after inclusion of `CPack.cmake` into `CMakeLists.txt`.
Closes: #19607
Found via `codespell -q 3 -I ../cmake-whitelist.txt --skip="./Utilities"`
where the whitelist consists of
```
aci
ans
behaviour
buil
convertor
dum
earch
ect
emmited
emmitted
helpfull
iff
isnt
ith
lowercased
mose
nd
nknown
nto
objext
ot
pathes
pevents
splitted
substract
superceded
supercedes
te
tim
todays
uint
upto
whitespaces
```
Ensure we use the `cmake` corresponding to the running `cpack`
even if it is not first in `PATH` or has had its name changed.
This was accidentally left out in commit v3.7.0-rc1~81^2 (CPack/RPM:
Generate source rpm (SRPM) packages on demand, 2016-09-19).
These modules are not meant to be included by user code, they are
only an internal implementation detail for CPack. Having them live
in the main Modules directory with documentation was misleading, so
they have been moved into Modules/Internal/CPack, and their
documentation has been stripped following its move into the new
"CPack Generators" section. No-op modules which contained only
documentation have been removed entirely.
The only module that hasn't been moved is CPackIFW, because it
contains user-facing macros which would be lost if it were moved.
So, the CPackIFW module has been updated with a note explaining what
needs to (eventually) happen.
