Can't compile a12

As I can’t get B2 running I’m trying to compile the version I know that did work on my end - a12. But I can’t compile linux host. Probably something trivial - as I’m not a programmer and I basically have no clue what is going on. During cmake part I see:

fatal: not a git repository (or any parent up to mount point /)
Stopping at filesystem boundary (GIT_DISCOVERY_ACROSS_FILESYSTEM not set)

While if I proceed with make I get:

/home/przemekj/Dokumenty/Github/LookingGlass-a12/client/spice/spice.c:39:10: fatal error: spice/error_codes.h: Nie ma takiego pliku ani katalogu
39 | #include <spice/error_codes.h>
| ^~~~~~~~~~~~~~~~~~~~~
compilation terminated.
make[2]: *** [CMakeFiles/looking-glass-client.dir/build.make:161: CMakeFiles/looking-glass-client.dir/spice/spice.c.o] Błąd 1
make[1]: *** [CMakeFiles/Makefile2:96: CMakeFiles/looking-glass-client.dir/all] Błąd 2
make: *** [Makefile:104: all] Błąd 2

Any suggestions what can I try doing to make it work?

Version a12 is very old and many bugs have been squashed since then. It’s not even available for downloads any longer. It relies on OS provided header files for spice that have since been removed from the OS. You should try your best to get the stable version working.