CircleCI: run scan-build and publish its results automatically

CircleCI is a continuous integration system like Travis CI, which
provides different features. Contrary to Travis CI, it is quite harder
to build the project with several build configurations (so it is not a
replacement), but it provides short-term storage for files produced by a
build job in what is called "artifacts".

Use this feature in order to store the results of clang's static
analyzer (scan-build) after every pushed commit. This way makes it
possible to quickly compare the result of the analyzer after applying
some patches that were sent for review to the mailing list, as it no
longer requires running the analyzer several times on the development
machine.

An output example is available at
https://352-118970575-gh.circle-artifacts.com/0/output-scan-build/2019-09-21-164945-6152-1/index.html
These web pages were created by the job described at
https://circleci.com/gh/fishilico/selinux/352

Signed-off-by: Nicolas Iooss <nicolas.iooss@m4x.org>

.circleci/config.yml

@@ -0,0 +1,40 @@
+# Configuration file for https://circleci.com/
+
+version: 2
+
+jobs:
+  build:
+    docker:
+      # Use a Python image from https://hub.docker.com/r/circleci/python/tags/
+      - image: circleci/python:3.6
+
+    steps:
+    - checkout
+
+    # Install dependencies
+    - run: sudo apt-get update -qq
+    - run: sudo apt-get install -qq bison clang clang-tools flex gawk gettext libaudit-dev libcap-dev libcap-ng-dev libcunit1-dev libdbus-glib-1-dev libpcre3-dev python3-dev python-dev ruby-dev swig xmlto
+
+    - run:
+        name: Setup environment variables
+        command: |
+          echo 'export DESTDIR=$HOME/destdir' >> "$BASH_ENV"
+
+    # Download and install refpolicy headers for sepolgen tests
+    - run:
+        name: Download refpolicy Makefile
+        command: |
+          curl --location --retry 10 -o refpolicy.tar.bz2 https://github.com/SELinuxProject/refpolicy/releases/download/RELEASE_2_20180701/refpolicy-2.20180701.tar.bz2
+          tar -xvjf refpolicy.tar.bz2
+          sed -e "s,^PREFIX :=.*,PREFIX := $DESTDIR/usr," -i refpolicy/support/Makefile.devel
+          sudo make -C refpolicy install-headers
+          sudo mkdir -p /etc/selinux
+          echo 'SELINUXTYPE=refpolicy' | sudo tee /etc/selinux/config
+          echo 'SELINUX_DEVEL_PATH = /usr/share/selinux/refpolicy' | sudo tee /etc/selinux/sepolgen.conf
+          sed -e "s,\"\(/usr/bin/[cs]\),\"$DESTDIR\1," -i python/sepolgen/src/sepolgen/module.py
+
+    # Run clang's scan-build and store the result as artifacts
+    - run: ./scripts/run-scan-build
+    - store_artifacts:
+        path: scripts/output-scan-build
+        destination: output-scan-build