Changing path to pm_common directory in file pm_commom/CMakeLists.txt

[AntoineDelaby]

Changing the line $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/pm_common> of pm_common/CMakeLists.txt file to $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>.

With previous configuration, the build could not compile correctly because the specified path ${CMAKE_CURRENT_SOURCE_DIR}> points already to the pm_commom/ directory.

[rbdannenberg]

I'm not using or testing any of the BUILD_INTERFACE mechanisms, so I'm relying on contributors here. (Thanks!) This change looks sensible, although I'm worried that it will break things for others. If that's the case, let's add some required conditions and state assumptions about the build environment so we can properly test it and recommend "best practices". (Note that Github's automated builds work on multiple platforms before AND after the change.)