CI breakage for the reproducible wheels using extensions

[kushaldas]

Our CI for reproducible wheels is using CircleCI's Python 3.7 container image. Which installs the latest Python from source, thus it has a different version of Python and also totally different CFLAGS.

https://circleci.com/api/v1.1/project/github/freedomofpress/securedrop-debian-packaging/8970/output/102/0?file=true&allocation-id=60e3091a6147e451fc8f1ff6-0-build%2F52B5BD2F contains one such example failure.

Below are the values from container:

 'PY_BUILTIN_MODULE_CFLAGS': '-Wno-unused-result -Wsign-compare -DNDEBUG -g '
                             '-fwrapv -O3 -Wall -std=c99 -Wextra '
                             '-Wno-unused-result -Wno-unused-parameter '
                             '-Wno-missing-field-initializers '
                             '-Wno-cast-function-type '
                             '-Werror=implicit-function-declaration '
                             '-fprofile-use -fprofile-correction -I. '
                             '-I./Include -fPIC -DPy_BUILD_CORE_BUILTIN',
 'PY_CFLAGS': '-Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall',
 'PY_CFLAGS_NODIST': '-std=c99 -Wextra -Wno-unused-result '
                     '-Wno-unused-parameter -Wno-missing-field-initializers '
                     '-Wno-cast-function-type '
                     '-Werror=implicit-function-declaration -fprofile-use '
                     '-fprofile-correction',
 'PY_COERCE_C_LOCALE': 1,
 'PY_CORE_CFLAGS': '-Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 '
                   '-Wall -std=c99 -Wextra -Wno-unused-result '
                   '-Wno-unused-parameter -Wno-missing-field-initializers '
                   '-Wno-cast-function-type '
                   '-Werror=implicit-function-declaration -fprofile-use '
                   '-fprofile-correction -I. -I./Include -fPIC -DPy_BUILD_CORE',

And here are the values from a standard Debian Buster system

 'PY_BUILTIN_MODULE_CFLAGS': '-Wno-unused-result -Wsign-compare -DNDEBUG -g '
                             '-fwrapv -O2 -Wall -g   -fstack-protector-strong '
                             '-Wformat -Werror=format-security  -g -flto '
                             '-fuse-linker-plugin -ffat-lto-objects -std=c99 '
                             '-Wextra -Wno-unused-result -Wno-unused-parameter '
                             '-Wno-missing-field-initializers '
                             '-Wno-cast-function-type '
                             '-Werror=implicit-function-declaration -IObjects '
                             '-IInclude -IPython -I. -I../Include -Wdate-time '
                             '-D_FORTIFY_SOURCE=2 -fPIC '
                             '-DPy_BUILD_CORE_BUILTIN',
 'PY_CFLAGS': '-Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O2 -Wall '
              '-g   -fstack-protector-strong -Wformat -Werror=format-security  '
              '-g -flto -fuse-linker-plugin -ffat-lto-objects',
 'PY_CFLAGS_NODIST': '-std=c99 -Wextra -Wno-unused-result '
                     '-Wno-unused-parameter -Wno-missing-field-initializers '
                     '-Wno-cast-function-type '
                     '-Werror=implicit-function-declaration',
 'PY_COERCE_C_LOCALE': 1,
 'PY_CORE_CFLAGS': '-Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O2 '
                   '-Wall -g   -fstack-protector-strong -Wformat '
                   '-Werror=format-security  -g -flto -fuse-linker-plugin '
                   '-ffat-lto-objects -std=c99 -Wextra -Wno-unused-result '
                   '-Wno-unused-parameter -Wno-missing-field-initializers '
                   '-Wno-cast-function-type '
                   '-Werror=implicit-function-declaration -IObjects -IInclude '
                   '-IPython -I. -I../Include -Wdate-time -D_FORTIFY_SOURCE=2 '
                   '-fPIC -DPy_BUILD_CORE',
 'PY_CPPFLAGS': '-IObjects -IInclude -IPython -I. -I../Include -Wdate-time '
                '-D_FORTIFY_SOURCE=2',