Fix CMake warning and error message types

[mabelzhang]

🦟 Bug fix

Fix CMake warning and error message types, so that they're printed to the terminal during the build.

Summary

In a fresh build when I don't have all the dependencies, I'm getting a line that tells me to see BUILD ERRORS above, but there's nothing printed "above."
It's a dependency error, and it's only printed in stdout and not stderr.
So unless I have convenient access to the log directory (which I don't when building from a Dockerfile), I wouldn't know what package was missing without digging.

Step 15/15 : RUN cd ${IGN_WS}  && colcon build --merge-install --cmake-args -DBUILD_TESTING=OFF
 ---> Running in 623c9c1ecab6
Starting >>> ignition-cmake2
Starting >>> ignition-tools
Finished <<< ignition-cmake2 [1.23s]
Starting >>> ignition-math6
--- stderr: ignition-tools
CMake Error at CMakeLists.txt:231 (message):
  Errors encountered in build.  Please see the BUILD ERRORS above.


---
Failed   <<< ignition-tools [1.27s, exited with code 1]
Aborted  <<< ignition-math6 [1.72s]

Summary: 1 package finished [3.30s]
  1 package failed: ignition-tools
  1 package aborted: ignition-math6
  2 packages had stderr output: ignition-math6 ignition-tools
  12 packages not processed
The command '/bin/sh -c cd ${IGN_WS}  && colcon build --merge-install --cmake-args -DBUILD_TESTING=OFF' returned a non-zero code: 1

Upon entering the container and checking, log/latest/ignition-tools/stderr.log only has two lines:

CMake Error at CMakeLists.txt:231 (message):
  Errors encountered in build.  Please see the BUILD ERRORS above.

whereas stdout.log has these lines:

-- BUILD WARNINGS
--  ronn not found, manpages won't be generated
-- END BUILD WARNINGS

-- BUILD ERRORS: These must be resolved before compiling.
--  Missing: ruby (ruby)
-- END BUILD ERRORS

-- Configuring incomplete, errors occurred!
See also "/home/developer/ign_ws/build/ignition-tools/CMakeFiles/CMakeOutput.log".

After the fix, the output looks like:

$ colcon build --merge-install --cmake-args -DBUILD_TESTING=OFF
Starting >>> ignition-cmake2
Starting >>> ignition-tools
--- stderr: ignition-tools
CMake Warning at CMakeLists.txt:209 (message):
  BUILD WARNINGS


CMake Warning at CMakeLists.txt:211 (message):
    ronn not found, manpages won't be generated


CMake Warning at CMakeLists.txt:213 (message):
  END BUILD WARNINGS



CMake Error at CMakeLists.txt:226 (message):
  BUILD ERRORS: These must be resolved before compiling.


CMake Error at CMakeLists.txt:228 (message):
    Missing: ruby (ruby)


CMake Error at CMakeLists.txt:230 (message):
  END BUILD ERRORS



CMake Error at CMakeLists.txt:231 (message):
  Errors encountered in build.  Please see the BUILD ERRORS above.


---
Failed   <<< ignition-tools [0.13s, exited with code 1]
Aborted  <<< ignition-cmake2 [0.46s]

Checklist

• Signed all commits for DCO
• Added tests
• Updated documentation (as needed)
• Updated migration guide (as needed)
• codecheck passed (See contributing)
• All tests passed (See test coverage)
• While waiting for a review on your PR, please help review another open pull request to support the maintainers

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[chapulina]

Nice catch, this looks reasonable to me.

I wonder if ign-cmake could use the same fix here.