[develop2] fixing transitive linux libraries cmake

[memsharded]

Changelog: Fix: Fixing transitive shared linux libraries in CMakeDeps.

Close #13000

There were an issue where building against transitive shared dependencies in Linux (several transitive levels), was failing when this happens in different machines (need to upload & install in a different machine to reproduce), because the linker wants information about the libs, even if not strictly necessary to the final consumer application.

The approach that seems to work is:

• Add INTERFACE_LINK_DIRECTORIES to each target creation
• Make sure that the traits in CMakeDeps do not invalidate self.lib_paths, only libs to still avoiding direct linking.

This might need to extend to components too.

[jcar87]

I'm a bit confused - I think this would only solve the problem in some cases, but not all.

If the INTERFACE_LINK_DIRECTORIES property eventually maps to cmake passing -L entries to the. linker, the linker documentation (https://linux.die.net/man/1/ld) for -L states that these only apply to libraries linked via -l. This is relevant since the linker will not search in -L directories for "indirect" transitive runtime dependencies that are also not expressed in the linker flags.

That's what -rpath or -rpath-link achieves that -L doesn't (-rpath works ok when not cross building, -rpath-link is needed when a sysroot is also passed).

[memsharded]

The command for creating app in my test is:

/usr/bin/cmake -E cmake_link_script CMakeFiles/app.dir/link.txt --verbose=1
/usr/bin/g++ -m64 -O3 -DNDEBUG -m64 CMakeFiles/app.dir/src/app.cpp.o -o app   -L"/tmp/tmpbiy1ou19conans/path with spaces/.conan2/p/31071b4017b74cd1/p/lib"  -L"/tmp/tmpbiy1ou19conans/path with spaces/.conan2/p/bbd4a1e27c1d25cc/p/lib" 

 -Wl,-rpath,"/tmp/tmpbiy1ou19conans/path with spaces/.conan2/p/31071b4017b74cd1/p/lib:/tmp/tmpbiy1ou19conans/path with spaces/.conan2/p/bbd4a1e27c1d25cc/p/lib" 

"/tmp/tmpbiy1ou19conans/path with spaces/.conan2/p/31071b4017b74cd1/p/lib/libchat.so"

I have isolated the -Wl, -rpath line, that contains 2 entries, for chat and hello.