"build_bootloader.sh" doesn't exist and "walkoff.sh up --build" fails about walkoff HOT 3 CLOSED

UMPIRE - DEBUG:Step 9/13 : RUN pip install --no-warn-script-location --prefix="/install" -r /requirements.txt
...
UMPIRE - DEBUG:Downloading https://files.pythonhosted.org/packages/be/60/da377e1bed002716fb2d5d1d1cab720f298cb33ecff7bf7adea72788e4e4/cryptography-2.8.tar.gz (504kB)
UMPIRE - DEBUG:Installing build dependencies: started
UMPIRE - DEBUG:Installing build dependencies: finished with status 'error'
UMPIRE - DEBUG:  ERROR: Command errored out with exit status 1:
...
c/_cffi_backend.c:15:10: fatal error: ffi.h: No such file or directory
       #include <ffi.h>
                ^~~~~~~
      compilation terminated.
      error: command 'gcc' failed with exit status 1
...
UMPIRE - ERROR:The command '/bin/sh -c pip install --no-warn-script-location --prefix="/install" -r /requirements.txt' returned a non-zero code: 1

UMPIRE - DEBUG:Preparing to unpack .../00-perl-modules-5.28_5.28.1-6_all.deb ...
UMPIRE - DEBUG:Unpacking perl-modules-5.28 (5.28.1-6) ...
UMPIRE - DEBUG:Running setup.py install for multidict: finished with status 'error'
UMPIRE - DEBUG:    ERROR: Command errored out with exit status 1:
     command: /usr/local/bin/python -u -c 'import sys, setuptools, tokenize; sys.argv[0] = '"'"'/tmp/pip-install-asqaj_7e/multidict/setup.py'"'"'; __file__='"'"'/tmp/pip-install-asqaj_7e/multidict/setup.py'"'"';f=getattr(tokenize, '"'"'open'"'"', open)(__file__);code=f.read().replace('"'"'\r\n'"'"', '"'"'\n'"'"');f.
close();exec(compile(code, __file__, '"'"'exec'"'"'))' install --record /tmp/pip-record-f_pxx0ji/install-record.txt --single-version-externally-managed --prefix /install --compile
         cwd: /tmp/pip-install-asqaj_7e/multidict/
...
building 'multidict._multidict' extension
    creating build/temp.linux-armv7l-3.7
    creating build/temp.linux-armv7l-3.7/multidict
    gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -I/usr/local/include/python3.7m -c multidict/_multidict.c -o build/temp.linux-armv7l-3.7/multidict/_multidict.o -O2 -std=c99 -Wall -Wsign-compare -Wconversion -fno-strict-aliasing -pedantic
    unable to execute 'gcc': No such file or directory
    error: command 'gcc' failed with exit status 1