CI: Do the CMake native debug build from an Autotools make dist

We officially release dbus in the form of Autotools `make dist` tarballs,
but people who have downloaded those tarballs should be able to choose
the CMake build system. Our CI should assert that they can.

(The Autotools debug build already does a `make distcheck`, which
asserts that tarball releases can be used for an Autotools build.)

Signed-off-by: Simon McVittie <smcv@collabora.com>
Resolves: dbus#255

.gitlab-ci.yml

@@ -82,7 +82,7 @@ build:cmake:
   stage: build
   image: "debian:stretch-slim"
   variables:
-    ci_buildsys: "cmake"
+    ci_buildsys: "cmake-dist"
   script: *script
 
 build:i686-w64-mingw32-debug:

.travis.yml

@@ -32,7 +32,7 @@ env:
   - ci_variant=debug
   - ci_variant=reduced
   - ci_variant=legacy
-  - ci_buildsys=cmake
+  - ci_buildsys=cmake-dist
   - ci_host=i686-w64-mingw32
   - ci_host=i686-w64-mingw32 ci_buildsys=cmake ci_variant=debug
   - ci_host=x86_64-w64-mingw32 ci_variant=debug

tools/ci-build.sh

@@ -101,6 +101,19 @@ maybe_fail_tests () {
 # own checks.
 NOCONFIGURE=1 ./autogen.sh
 
+case "$ci_buildsys" in
+    (cmake-dist)
+        # Do an Autotools `make dist`, then build *that* with CMake,
+        # to assert that our official release tarballs will be enough
+        # to build with CMake.
+        mkdir ci-build-dist
+        ( cd ci-build-dist; ../configure )
+        make -C ci-build-dist dist
+        tar --xz -xvf ci-build-dist/dbus-1.*.tar.xz
+        cd dbus-1.*/
+        ;;
+esac
+
 srcdir="$(pwd)"
 mkdir ci-build-${ci_variant}-${ci_host}
 cd ci-build-${ci_variant}-${ci_host}
@@ -287,7 +300,7 @@ case "$ci_buildsys" in
         fi
         ;;
 
-    (cmake)
+    (cmake|cmake-dist)
         case "$ci_host" in
             (*-w64-mingw32)
                 set _ "$@"