I figured out the reasons for the error.
This solution applies to all operating system, not just the Rasberry PI. (Excludes clause about swap file increase.)
I ran the installer for version 4.0.0, even though I copied version 3.4.4 from the repository.
\$ sudo -s
# git clone https://github.com/phalcon/cphalcon
# cd cphalcon/
# git checkout tags/v3.4.4 ./
# zephir fullclean
# zephir build
But it had to be done:
\$ sudo -s
# git clone https://github.com/phalcon/cphalcon
# cd cphalcon/
# git checkout tags/v3.4.4 ./
# cd build
# ./install
If you need version 4.0.0, then we must do as is written in the manual for 4.0.0, a little tweak version
\$ sudo -s
# git clone https://github.com/phalcon/cphalcon
# cd cphalcon/
# git checkout tags/v4.0.0-beta.1 ./
# zephir fullclean
# zephir build
And also, it was necessary to increase the swap file from default 100 MB to at least 2000 MB.
Because, the compiler lacks RAM. 1 GB.
\$ sudo -s
# nano /etc/dphys-swapfile
Replacing CONF_SWAPSIZE=100 with CONF_SWAPSIZE=2000
And having saved the setting, we reboot the daemon:
# /etc/init.d/dphys-swapfile stop
# /etc/init.d/dphys-swapfile start