Try and fix broken 32bit qemu builds on 64bit system

This patch adds a 'fix' for trying to build on armv7 32bit system
from a 64bit system.  qemu seems broken in this case.

.github/workflows/master-build.yml

@@ -56,6 +56,7 @@ jobs:
         file: ./Dockerfile-dev
         build-args: |
             BRANCH=${{ steps.branch-name.outputs.current_branch }}
+            BUILDX_QEMU_ENV=true
         push: true
         tags: |
           hemna6969/aprsd:${{ steps.branch-name.outputs.current_branch }}

.github/workflows/release_build.yml

@@ -39,10 +39,11 @@ jobs:
       uses: docker/build-push-action@v3
       with:
         context: "{{defaultContext}}:docker"
-        platforms: linux/amd64,linux/arm64
+        platforms: linux/amd64,linux/arm64,linux/arm/v7
         file: ./Dockerfile
         build-args: |
             VERSION=${{ inputs.aprsd_version }}
+            BUILDX_QEMU_ENV=true
         push: true
         tags: |
           hemna6969/aprsd:v${{ inputs.aprsd_version }}

docker/Dockerfile

@@ -7,6 +7,7 @@ ARG UID
 ARG GID
 ARG TZ
 ARG VERSION=2.6.0
+ARG BUILDX_QEMU_ENV
 ENV APRS_USER=aprs
 ENV HOME=/home/aprs
 ENV TZ=${TZ:-US/Eastern}
@@ -26,6 +27,14 @@ RUN apt install -y python3 python3-pip python3-dev python3-lxml
 RUN addgroup --gid $GID $APRS_USER
 RUN useradd -m -u $UID -g $APRS_USER $APRS_USER
 
+# Handle an extremely specific issue when building the cryptography package for
+# 32-bit architectures within QEMU running on a 64-bit host (issue #30).
+RUN if [ "${BUILDX_QEMU_ENV}" = "true" -a "$(getconf LONG_BIT)" = "32" ]; then \
+        pip3 install -U cryptography==3.3.2; \
+    else \
+        pip3 install cryptography ;\
+    fi
+
 # Install aprsd
 RUN pip install aprsd==$APRSD_PIP_VERSION
 

docker/Dockerfile-dev

@@ -6,6 +6,8 @@ ARG BRANCH=master
 ARG UID
 ARG GID
 
+ARG BUILDX_QEMU_ENV
+
 ENV APRS_USER=aprs
 ENV HOME=/home/aprs
 ENV APRSD=http://github.com/craigerl/aprsd.git
@@ -39,6 +41,13 @@ RUN cat $HOME/.bashrc
 
 USER root
 WORKDIR $HOME
+# Handle an extremely specific issue when building the cryptography package for
+# 32-bit architectures within QEMU running on a 64-bit host (issue #30).
+RUN if [ "${BUILDX_QEMU_ENV}" = "true" -a "$(getconf LONG_BIT)" = "32" ]; then \
+        pip3 install -U cryptography==3.3.2; \
+    else \
+        pip3 install cryptography ;\
+    fi
 RUN mkdir $INSTALL
 RUN git clone -b $BRANCH $APRSD $INSTALL/aprsd
 RUN    cd $INSTALL/aprsd && pip3 install -v .

docker/build.sh

@@ -88,12 +88,15 @@ then
     # Use this script to locally build the docker image
     docker buildx build --push --platform $PLATFORMS \
         -t harbor.hemna.com/hemna6969/aprsd:$TAG \
-        -f Dockerfile-dev --build-arg branch=$BRANCH --no-cache .
+        -f Dockerfile-dev --build-arg branch=$BRANCH \
+        --build-arg BUILDX_QEMU_ENV=true \
+        --no-cache .
 else
     # Use this script to locally build the docker image
     echo "Build with tag=${TAG} BRANCH=${BRANCH} dev?=${DEV} platforms?=${PLATFORMS} VERSION=${VERSION}"
     docker buildx build --push --platform $PLATFORMS \
         --build-arg VERSION=$VERSION \
+        --build-arg BUILDX_QEMU_ENV=true \
         -t hemna6969/aprsd:$VERSION \
         -t hemna6969/aprsd:$TAG \
         -t hemna6969/aprsd:latest \