[qt5base] Add libatomic to qt5base-core DEPENDS

[titobrasolin]

I encountered a compilation error for qt5base-core on the main branch due to a missing libatomic.so.1 dependency:

Package qt5base-core is missing dependencies for the following libraries:
libatomic.so.1

This library is provided by the libatomic package.

Please add +libatomic to the DEPENDS line for qt5base-core in qt5base/Makefile.

Example change:

DEPENDS+=+libatomic +libpthread ...

@mirko, bringing this to your attention for Qt5 packages.

Thanks!