[signer] Allow for use as a pcscd service container

GitHub Actions does not (yet) allow for specifying a command for a
service container.  Work around this by allowing pcscd to be invoked
by passing a non-empty environment variable "RUN_PCSCD".

Signed-off-by: Michael Brown <mbrown@fensystems.co.uk>

Author: mcb30

signer/Dockerfile

@@ -19,6 +19,12 @@ RUN echo "install_weak_deps=False" >> /etc/dnf/dnf.conf \
 	syslinux \
     && dnf clean all -y
 
+COPY entrypoint.sh /bin/entrypoint.sh
+
+ENTRYPOINT [ "/bin/entrypoint.sh" ]
+
+CMD [ "/bin/sh" ]
+
 FROM signer AS check-signer
 
 RUN dnf install -y \

signer/entrypoint.sh

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+# GitHub Actions does not (yet) allow for specifying a command for a
+# service container.  Work around this by allowing pcscd to be invoked
+# by passing a non-empty environment variable "RUN_PCSCD".
+#
+if [ -n "${RUN_PCSCD}" ] ; then
+    rm -f /run/pcscd/pcscd.comm
+    exec /usr/bin/pcscd --foreground --disable-polkit
+fi
+
+exec "$@"