% git clone https://github.com/nop00/shipping-is-a-feature/i
% cd shipping-is-a-feature
% pceas demo.asm
PC Engine Assembler 3.22, Dec 7 2016)

pass 1
#[1] demo.asm
78 :O000 .include "../_funcs.asm"
Can not open file!

1 error(s)

% p ../meet-the-supergrafx/_funcs.asm .
% ls -alFh
total 3240
drwxr-xr-x 51 grey staff 1.7K Dec 7 09:01 ./
drwxr-xr-x 6 grey staff 204B Dec 7 09:05 ../
drwxr-xr-x 13 grey staff 442B Dec 7 08:56 .git/
-rw-r--r-- 1 grey staff 6.6K Dec 7 08:56 README.md
-rw-r--r-- 1 grey staff 34K Dec 7 08:56 _font.asm
-rw-r--r-- 1 grey staff 69B Dec 7 09:03 _funcs.asm
-rw-r--r-- 1 grey staff 6.8K Dec 7 08:56 _macros.asm
-rw-r--r-- 1 grey staff 2.0K Dec 7 08:56 _macrosbase.asm
-rw-r--r-- 1 grey staff 1.5K Dec 7 08:56 _sound.asm
-rw-r--r-- 1 grey staff 485B Dec 7 08:56 _transition.asm
drwxr-xr-x 10 grey staff 340B Dec 7 08:56 azasel/
-rw-r--r-- 1 grey staff 27K Dec 7 08:56 buenzli_bg.asm
-rw-r--r-- 1 grey staff 68K Dec 7 08:56 buenzli_bg_data.asm
-rw-r--r-- 1 grey staff 170K Dec 7 08:56 buenzli_bg_data2.asm
-rw-r--r-- 1 grey staff 4.2K Dec 7 08:56 common.asm
-rw-r--r-- 1 grey staff 11K Dec 7 08:56 credits.asm
-rw-r--r-- 1 grey staff 54K Dec 7 08:56 credits_data1.asm
-rw-r--r-- 1 grey staff 55K Dec 7 08:56 credits_data2.asm
-rw-r--r-- 1 grey staff 71K Dec 7 08:56 credits_data3.asm
-rw-r--r-- 1 grey staff 27K Dec 7 08:56 credits_data4.asm
-rw-r--r-- 1 grey staff 7.3K Dec 7 08:56 credits_data5.asm
-rw-r--r-- 1 grey staff 8.4K Dec 7 08:56 demo.asm
-rw-r--r-- 1 grey staff 4.7K Dec 7 08:56 demo_logo.asm
-rw-r--r-- 1 grey staff 84K Dec 7 08:56 demo_logo_data.asm
-rw-r--r-- 1 grey staff 53K Dec 7 08:56 demo_logo_data2.asm
-rw-r--r-- 1 grey staff 21K Dec 7 08:56 demo_logo_data3.asm
-rw-r--r-- 1 grey staff 341B Dec 7 08:56 fadetowhite.asm
-rw-r--r-- 1 grey staff 23K Dec 7 08:56 font01.asm
-rw-r--r-- 1 grey staff 21K Dec 7 08:56 font02.asm
-rw-r--r-- 1 grey staff 19K Dec 7 08:56 fontasteroids.asm
-rw-r--r-- 1 grey staff 2.4K Dec 7 08:56 goodbye.asm
-rw-r--r-- 1 grey staff 77K Dec 7 08:56 goodbye_data.asm
-rw-r--r-- 1 grey staff 10K Dec 7 08:56 greets.asm
-rw-r--r-- 1 grey staff 50K Dec 7 08:56 greets_data.asm
-rw-r--r-- 1 grey staff 94K Dec 7 08:56 greets_data2.asm
-rw-r--r-- 1 grey staff 9.6K Dec 7 08:56 greets_data3.asm
drwxr-xr-x 13 grey staff 442B Dec 7 08:56 music/
-rw-r--r-- 1 grey staff 4.1K Dec 7 08:56 punkfloyd_logo.asm
-rw-r--r-- 1 grey staff 75K Dec 7 08:56 punkfloyd_logo_data.asm
-rw-r--r-- 1 grey staff 6.1K Dec 7 08:56 rasters.asm
-rw-r--r-- 1 grey staff 59K Dec 7 08:56 rasters_data.asm
-rw-r--r-- 1 grey staff 55K Dec 7 08:56 transitions.asm
-rw-r--r-- 1 grey staff 2.7K Dec 7 08:56 warning.asm
-rw-r--r-- 1 grey staff 45K Dec 7 08:56 warning_data.asm
-rw-r--r-- 1 grey staff 54K Dec 7 08:56 warning_data2.asm
-rw-r--r-- 1 grey staff 47K Dec 7 08:56 warning_data3.asm
-rw-r--r-- 1 grey staff 31K Dec 7 08:56 wazza_data1.asm
-rw-r--r-- 1 grey staff 29K Dec 7 08:56 wazza_data2.asm
-rw-r--r-- 1 grey staff 31K Dec 7 08:56 wazza_data3.asm
-rw-r--r-- 1 grey staff 30K Dec 7 08:56 wazza_data4.asm
-rw-r--r-- 1 grey staff 31K Dec 7 08:56 wazza_data5.asm

% pceas demo.asm
PC Engine Assembler 3.22, Dec 7 2016)

pass 1
#[1] demo.asm
78 :O000 .include "../_funcs.asm"
Can not open file!

1 error(s)

So, it appears as though the _funcs.asm file expected by the demo.asm build is not present in this repository. However, even when copying that _funcs.asm file from another repository also by nop00 that is insufficient. Both meet-the-supergrafx and le-petit-chat-n-est-pas-mort produce demo.pce when pceas demo.asm is run (though I have not yet tested them in mednafen nor hardware yet presumably they will run correctly?) However, this repository seems to have issues and even presuming perhaps you shared a funcs.asm call between projects was perhaps naive, so at the moment I can't currently reproduce this build to test. :)