Fix : libcanfestival_unix.a not built if examples are not compiled

Problem: when building Canfestival with unix timers 'libcanfestiva_unix.a'
is built only if you build examples too.

Test case:

$ ./configure --timers=unix --can=socket --target=unix
$ make canfestival

...

no errors but 'libcanfestival_unix.a' is not built:
$ find . -name "*.a"
./src/libcanfestival.a

Changing line 90 of 'drivers/unix/Makefile.in' to:
#driver: $(OBJS)
driver: libcanfestival_$(TARGET).a

solves the problem:

$ ./configure --timers=unix --can=socket --target=unix
$ make canfestival

...

$ find . -name "*.a"
./drivers/unix/libcanfestival_unix.a
./src/libcanfestival.a

     1

[Desktop Entry]

     2

Encoding=UTF-8

     3

Name=CANOpen Object Dictionary Editor

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Name[fr]=Editeur de Dictionnaire d'Objets CANOpen

     5

Comment=Create, modifify, configure CANOpen nodes

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Comment[fr]=Créer, modifier, configurer des noeuds CANOpen

     7

Exec=/usr/bin/objdictedit

     8

Icon=/usr/share/CanFestival-3/objdictgen/networkedit.png

     9

Terminal=false

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MultipleArgs=false

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Type=Application

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Categories=Application;Development;

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StartupNotify=true

    14