CMake warning: empty command-line option

[dkroenke]

Required information

Operating system:
Ubuntu 20.04 LTS

Compiler version:
CMake 3.23.0 (Released on 29-03-2022)
GCC 9.4.0

Observed result or behaviour:
Taken from #1310 (comment)

When building iceoryx_posh with CMake 3.23, it throws a warning:

Ignoring empty string ("") provided on the command line.

This happens because when CMAKE_TOOLCHAIN_FILE is not
defined, TOOLCHAIN_FILE is also not defined and thus is empty.
Workaround this new behavior by setting a variable that contains
a bunch of things, and may also optionally include the
define for the TOOLCHAIN file, which removes the warning.

This is currently causing a warning in the ROS 2 buildfarm with Windows, like > https://ci.ros2.org/view/nightly/job/nightly_win_rel/2257/cmake/ . Note that I've targeted this to the release_2.0 branch, as that is what > we are using for ROS 2. If you'd prefer me to target to master, I'm happy to do that but then I'll request a backport to the release_2.0 > branch.

Build log:

--- stderr: iceoryx_posh
09:40:11 CMake Warning:
09:40:11   Ignoring empty string ("") provided on the command line.
09:40:11 
09:40:11 
09:40:11 ---
09:40:11 Finished <<< iceoryx_posh [2min 0s]

Expected result or behaviour:
No CMake warning shall be emitted.

Conditions where it occurred / Performed steps:

1. Download custom CMake version

   wget https://cmake.org/files/v3.23/cmake-3.22.0-linux-x86_64.sh
   

2. Set custom CMake bin path

   export PATH=/foo/bar/tmp/cmake-3.23.0-linux-x86_64/bin:$PATH
   

3. Build iceoryx with colcon

Note that this warning does not occur on cmake 3.22 or earlier.

Actions:

• Merge fix into release_2.0 branch thanks to @clalancette
• increase version number to 2.0.1 and add changelog entry
• set git tag v2.0.1 in iceoryx
• backport changes from release branch to master