[cmake] Use GNU install dirs variables instead of hardcoded value

[DownerCase]

Description

Removes hardcoded install destinations that aren't derived from the appropriate CMAKE_INSTALL_<DIR>, without this the special case CMAKE_INSTALL_PREFIX of / behaves incorrectly, with files split between (for example) /usr/include and /include

Replaces the following uses with their eCAL_install_<DIR> equivalents:

• INSTALL_LIB_DIR
• INSTALL_BIN_DIR
• INSTALL_INCLUDE_DIR
• INSTALL_CMAKE_DIR (was unused)

Moved the asioTargets.cmake from lib/CMake to lib/cmake consistent with elsewhere.

Gets hdf5 submodule to use the GNU install dirs.

C#: Removed the unused PUBLIC_HEADER install and simplified the install command to implicitly use the GNU install dirs (if available -- which they are because I added the include() for them).

This should only really make any difference at all when CMAKE_INSTALL_PREFIX is exactly /; which admittedly is rare and unusual. Beyond that, it does mean all the install paths are now user controllable.

Related issues

Cherry-pick to

• none

[KerstinKeller]

Thanks for making the PR!

The only concern I have, that by using the values in the ecal or lang/csharp subfolders, we will no longer be able to build these components on their own.
We could introduce eCAL_core_xxx directories, or use the CMAKE_INSTALL_... variables directly there.

Or, as I think that specifying the install directories is no longer required in CMake (I think they were before CMake 3.15, or so), maybe it could be deleted altogether.

[DownerCase]

Thanks for making the PR!

The only concern I have, that by using the values in the ecal or lang/csharp subfolders, we will no longer be able to build these components on their own. We could introduce eCAL_core_xxx directories, or use the CMAKE_INSTALL_... variables directly there.

Not sure what you mean w.r.t the ecal subfolder as eCAL core already uses the values (eg:

ecal/ecal/core/src/ecal_defs.h.in

Line 37 in 3b22b6e

#define ECAL_INSTALL_APP_DIR "@eCAL_install_app_dir@"

, https://github.com/eclipse-ecal/ecal-core/blob/e91a95c74fefc5e8d97eb19ed0788da022ed5e46/CMakeLists.txt#L154)

The csharp and python subfolders can't currently be built independently as they lack the requisite find_package(eCAL) calls (amongst other issues).

Or, as I think that specifying the install directories is no longer required in CMake (I think they were before CMake 3.15, or so), maybe it could be deleted altogether.

That's pretty accurate. For install(TARGETS ...) the docs note:

"For regular executables, static libraries and shared libraries, the DESTINATION argument is not required.
For these target types, when DESTINATION is omitted, a default destination will be taken from the appropriate variable from GNUInstallDirs, or set to a built-in default value if that variable is not defined."

For install(DIRECTORY ...) (i.e: old style method of install headers) "Either a TYPE or a DESTINATION must be provided, but not both." (and it will follow the same logic as above to pick a value)

[DownerCase]

Or, as I think that specifying the install directories is no longer required in CMake (I think they were before CMake 3.15, or so), maybe it could be deleted altogether.

I rebased and changed the C# folder to implicitly use the GNU install dir variables.

[KerstinKeller]

Thanks for performing this cleanup!