Dockerfile: Use Fedora 31

Update to the newest version.

Python 3 is now the default one, so we can drop the suffix from pip
invocation and we have to install it explicitly.

Cc: Petri Latvala <petri.latvala@intel.com>
Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Reviewed-by: Petri Latvala <petri.latvala@intel.com>

.gitlab-ci.yml

@@ -84,7 +84,7 @@ build:tests-fedora-oldest-meson:
   stage: build
   script:
     - dnf remove -y meson
-    - pip3 install /usr/src/meson-*.tar.gz
+    - pip install /usr/src/meson-*.tar.gz
     - meson $MESON_OPTIONS build
     - ninja -C build
     - ninja -C build igt-gpu-tools-doc

Dockerfile.build-fedora

-FROM fedora:30
+FROM fedora:31
 
 RUN dnf install -y \
 	gcc flex bison libatomic meson ninja-build xdotool \
@@ -37,10 +37,14 @@ RUN rm -fr /tmp/peg
 # For compile-testing on clang
 RUN dnf install -y clang
 
+# For test list comparison
+RUN dnf install -y diffutils
+
 # For the helpers for the container with IGT inside
 RUN dnf install -y findutils
 
 # Meson version switching shenanigans
+RUN dnf install -y python3-pip
 RUN curl -o "/usr/src/#1" "https://files.pythonhosted.org/packages/e8/ec/3e6a68c9e0fd4b4f4fb6877a3ccfb6f6e6d09f2b4fc87674e671bf64b7b8/{meson-0.47.2.tar.gz}"
 
 RUN dnf clean all