...
cc -c -pipe -fPIC -fvisibility=hidden -O -W -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wmissing-prototypes -Werror -g  -march=x86-64 -mtune=generic -O2 -pipe -fno-plt -I src -I build -I/usr/include/ruby-2.7.0/x86_64-linux -I/usr/include/ruby-2.7.0 \
-MMD -MF build/src/ruby/nxt_ruby-ruby.dep -MT build/src/ruby/nxt_ruby-ruby.o \
-o build/src/ruby/nxt_ruby-ruby.o src/ruby/nxt_ruby.c
src/ruby/nxt_ruby.c: In function ‘nxt_ruby_rack_result_body’:
src/ruby/nxt_ruby.c:714:23: error: passing argument 5 of ‘rb_block_call’ from incompatible pointer type [-Werror=incompatible-pointer-types]
  714 |                       nxt_ruby_rack_result_body_each, 0);
      |                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                       |
      |                       VALUE (*)(VALUE) {aka long unsigned int (*)(long unsigned int)}
In file included from /usr/include/ruby-2.7.0/ruby.h:33,
                 from src/ruby/nxt_ruby.h:11,
                 from src/ruby/nxt_ruby.c:6:
/usr/include/ruby-2.7.0/ruby/ruby.h:1985:47: note: expected ‘rb_block_call_func_t’ {aka ‘long unsigned int (*)(long unsigned int,  long unsigned int,  int,  const long unsigned int *, long unsigned int)’} but argument is of type ‘VALUE (*)(VALUE)’ {aka ‘long unsigned int (*)(long unsigned int)’}
 1985 | VALUE rb_block_call(VALUE,ID,int,const VALUE*,rb_block_call_func_t,VALUE);
      |                                               ^~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make: *** [build/Makefile:1825: build/src/ruby/nxt_ruby-ruby.o] Error 1

./configure --prefix=/usr \
            --sbindir=/usr/bin \
            --modules="/usr/lib/$pkgbase" \
            --state="/var/lib/$pkgbase" \
            --pid="/run/$pkgbase.pid" \
            --log="/var/log/$pkgbase.log" \
            --control="/run/$pkgbase.control.sock" \
            --openssl
./configure python --config=python3-config
./configure python --config=python2-config
./configure php
./configure perl
./configure ruby
./configure nodejs
./configure go --go-path=/usr/lib/go
make all