cstrans-df-run: ignore space after trailing backslash

Although it does not make any sense, `podman build` seems to do it as
well while parsing `Dockerfile`.  We need to emulate this behavior to
stay compatible.

Fixes: https://issues.redhat.com/browse/OSH-391

Author: kdudka

src/cstrans-df-run.cc

@@ -59,7 +59,7 @@ class DockerFileTransformer {
         const RE reLineRunExec_ = RE("^RUN  *\\[(.*)\\] *$");
 
         /// match ... in ... BS-NL
-        const RE reLineCont_    = RE("(^.*[^\\\\])\\\\$");
+        const RE reLineCont_    = RE("(^.*[^\\\\])\\\\ *$");
 
         /// match in-line comments
         const RE reComment_     = RE("^\\s*#.*$");

tests/cstrans-df-run/0010-stdout.txt

@@ -27,9 +27,7 @@ RUN ["/opt/cov-sa-2019.09/bin/cov-build", "--dir=/cov", "--append-log", "sh", "-
 
 # Rootless/unprivileged buildah configurations
 # https://github.com/containers/buildah/blob/main/docs/tutorials/05-openshift-rootless-build.md
-RUN ["/opt/cov-sa-2019.09/bin/cov-build", "--dir=/cov", "--append-log", "sh", "-c", "touch /etc/subgid /etc/subuid &&     chmod g=u /etc/subgid /etc/subuid /etc/passwd &&     echo 'podman:100000:65536' > /etc/subuid && echo 'podman:100000:65536' > /etc/subgid && \tmkdir -p /home/podman/.config/containers &&     (echo '[storage]';echo 'driver = \"vfs\"') > /home/podman/.config/containers/storage.conf && \\ "]
-    sed -i 's/short-name-mode="enforcing"/short-name-mode="permissive"/g' /etc/containers/registries.conf && \
-	mkdir /certs /home/podman/.config/cni && chown podman:podman /certs /home/podman/.config/cni
+RUN ["/opt/cov-sa-2019.09/bin/cov-build", "--dir=/cov", "--append-log", "sh", "-c", "touch /etc/subgid /etc/subuid &&     chmod g=u /etc/subgid /etc/subuid /etc/passwd &&     echo 'podman:100000:65536' > /etc/subuid && echo 'podman:100000:65536' > /etc/subgid && \tmkdir -p /home/podman/.config/containers &&     (echo '[storage]';echo 'driver = \"vfs\"') > /home/podman/.config/containers/storage.conf &&     sed -i 's/short-name-mode=\"enforcing\"/short-name-mode=\"permissive\"/g' /etc/containers/registries.conf && \tmkdir /certs /home/podman/.config/cni && chown podman:podman /certs /home/podman/.config/cni"]
 
 VOLUME ["/tmp", "/certs"]