Patch to check for atomic support during build

Instead of building with -Wl,--as-needed -latomic an all architectures,
this dynamically detects the need for linking against libatomic. This is
cleaner.

The previous approach of setting the linker flags with
DEB_LDFLAGS_MAINT_APPEND added the flags to early on the command line so
that not all objects were linked against libatomic. This lead to build
failures on at least mips and mipsel.

Closes: #913601