Fix building RSL inside a workspace while it's already installed at a system level

[ChrisThrasher]

We've received informal reports that after removing ament, RSL can no longer be built and used inside a Colcon workspace when another version is already installed at a system level. I'm not sure what it is about ament CMake macros that fixes this but there seems to be a correlation there that we need to dig in to.

[tylerjw]

As far as I can tell, the issue is with the wrong headers being used at compile time.

[ChrisThrasher]

Something I want to check is to compare the INTERFACE_INCLUDE_DIRECTORIES for rsl::rsl on the current HEAD of main against an older version when we still used ament. I'd expect those to be the same but if not then we have something to look in to.

[traversaro]

Not sure if this is helpful, but perhaps it could be helpful to pass BEFORE to target_include_Directories in

RSL/CMakeLists.txt

Lines 26 to 29 in 549df46

	target_include_directories(rsl PUBLIC
	$<BUILD_INTERFACE:${PROJECT_SOURCE_DIR}/include>
	$<BUILD_INTERFACE:${PROJECT_BINARY_DIR}/include>
	)

. However, I have no idea why things would be different with ament_cmake .

[ChrisThrasher]

If someone can reproduce this problem I'd love to try that out. The hard part is getting a build environment that recreates this error. I don't have that on hand at the moment.