append to compile flags instead of overwriting

CFLAGS and LDFLAGS may be passed in by an upstream build system. we
want to make sure we absolutely add our dependency flags otherwise
stuff like hardening flags will break the build

Closes: xorg62#29

Merge pull request xorg62#41 from anarcat/fixdelay

set time structure at the right moment

Merge pull request xorg62#25 from jcvernaleo/master

Allow C and LD flags to be overwritten.

tag v0.1

Tag release v2.0

make this build with --as-needed, see Debian BTS #647316

make clean succeed all the time