`make distcheck` fails

[GerHobbelt]

See CI: github actions.

Making all in lib
make[2]: Entering directory '/home/runner/work/gup/gup/gup-0.0.7/_build/sub/lib'
gcc -DHAVE_CONFIG_H -I. -I../../../lib -I../include  -I./include -I../../../include   -g -O2 -Wall -W -Wpointer-arith -Wstrict-prototypes -Wmissing-declarations -MT gup_err.o -MD -MP -MF .deps/gup_err.Tpo -c -o gup_err.o ../../../lib/gup_err.c
mv -f .deps/gup_err.Tpo .deps/gup_err.Po
gcc -DHAVE_CONFIG_H -I. -I../../../lib -I../include  -I./include -I../../../include   -g -O2 -Wall -W -Wpointer-arith -Wstrict-prototypes -Wmissing-declarations -MT gup_io.o -MD -MP -MF .deps/gup_io.Tpo -c -o gup_io.o ../../../lib/gup_io.c
In file included from ../../../lib/gup_io.c:46:
../../../include/gup.h:109:10: fatal error: compiler_intrinsics.h: No such file or directory
  109 | #include "compiler_intrinsics.h"
      |          ^~~~~~~~~~~~~~~~~~~~~~~
compilation terminated.
make[2]: *** [Makefile:381: gup_io.o] Error 1
make[2]: Leaving directory '/home/runner/work/gup/gup/gup-0.0.7/_build/sub/lib'
make[1]: Leaving directory '/home/runner/work/gup/gup/gup-0.0.7/_build/sub'
make[1]: *** [Makefile:405: all-recursive] Error 1
make: *** [Makefile:620: distcheck] Error 1
Error: Process completed with exit code 2.