Dockerfile: use ldconfig for dynamic libraries

The libseccomp and libpathrs libraries built by Dockerfile are installed
into $DYLIB_DIR/lib, which is only made known to the dynamic linker via
LD_LIBRARY_PATH. Yet runc init is executed with a clean environment, so
it can not find libpathrs.so.0 and dies, resulting in

	unable to start container process: can't copy bootstrap data
	to pipe: write init-p: broken pipe

As a result, "make integration" and some of "make unittest" fail.

Use ldconfig instead of LD_LIBRARY_PATH.

This went unnoticed because CI only builds the image, and never runs
tests in it. Add a quick smoke test (run.bats) to the release job, which
is the only one that builds the image.

Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

.github/workflows/validate.yml

@@ -305,6 +305,8 @@ jobs:
       # needs it.
     - name: build docker image
       run: make runcimage
+    - name: smoke test docker image
+      run: make integration TESTPATH=/run.bats
     - name: make releaseall
       run: make releaseall
     - name: upload artifacts

Dockerfile

@@ -75,7 +75,9 @@ RUN mkdir -p $DYLIB_DIR \
     && /tmp/script/build-libpathrs.sh "$LIBPATHRS_VERSION" $DYLIB_DIR $RELEASE_ARCHES
 ENV LIBPATHRS_VERSION=$LIBPATHRS_VERSION
 
-ENV LD_LIBRARY_PATH=$DYLIB_DIR/lib
+# Use ldconfig rather than LD_LIBRARY_PATH, since runc init does not inherit
+# the environment.
+RUN echo "$DYLIB_DIR/lib" > /etc/ld.so.conf.d/runc-dylibs.conf && ldconfig
 ENV PKG_CONFIG_PATH=$DYLIB_DIR/lib/pkgconfig
 
 # Prevent the "fatal: detected dubious ownership in repository" git complain during build.