Fix cmake installation by using GNUInstallDirs

[Ryanf55]

• Don't override GNUInstallDirs
• This allows setting local prefix with cmake at installation time
• Use the new method in CI
• Solves #328

[richiprosima]

Build status:

• Linux
• Windows

[pablogs9]

Please take a look to the CI

[Ryanf55]

Ok, looks like the isolated build doesn't work.

2: CMake Error at /home/jenkins/workspace/Micro-XRCE-DDS-Agent Manual Linux/build/temp_install/isolated/share/microxrcedds_agent/cmake/microxrcedds_agentConfig.cmake:53 (find_package):
2:   By not providing "Findfastcdr.cmake" in CMAKE_MODULE_PATH this project has
2:   asked CMake to find a package configuration file provided by "fastcdr", but
2:   CMake did not find one.
2: 
2:   Could not find a package configuration file provided by "fastcdr"
2:   (requested version 1.1.0) with any of the following names:
2: 
2:     fastcdrConfig.cmake
2:     fastcdr-config.cmake
2: 
2:   Add the installation prefix of "fastcdr" to CMAKE_PREFIX_PATH or set
2:   "fastcdr_DIR" to a directory containing one of the above files.  If
2:   "fastcdr" provides a separate development package or SDK, be sure it has
2:   been installed.
2: Call Stack (most recent call first):
2:   CMakeLists.txt:19 (find_package)
2: 
2: 
2: -- Configuring incomplete, errors occurred!
2: See also "/home/jenkins/workspace/Micro-XRCE-DDS-Agent Manual Linux/build/microxrcedds_agent-build/test/case/CMakeFiles/CMakeOutput.log".
2: CMake Error at /home/jenkins/workspace/Micro-XRCE-DDS-Agent Manual Linux/test/case/packaging/Packaging.cmake:27 (message):
2:   Error in find_package.

Is it unreasonable to switch to using a package manager like CPM or even FetchContent which supports version pinning? The custom method implemented seems to be doing the same thing. There are better ways than calling git directly from CMake