gitlab-ci: Install most packages from Debian buster

We now use the C frontend of GCC 8 instead of 6 (required tweaking the
before_script for the clang job). We cannot use the C++ frontend of GCC
7 or newer yet, because upstream GCC 7 changed some C++ name mangling
stuff in backwards incompatible ways, and LLVM < 6.0 packages aren't
available in buster.

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>

.gitlab-ci.yml

@@ -66,12 +66,13 @@ debian:
   artifacts:
     when: on_failure
     untracked: true
+  variables:
+    CCACHE_COMPILERCHECK: "content"
   # Use ccache transparently, and print stats before/after
   before_script:
     - export PATH="/usr/lib/ccache:$PATH"
     - export CCACHE_BASEDIR="$PWD"
     - export CCACHE_DIR="$PWD/ccache"
-    - export CCACHE_COMPILERCHECK=content
     - ccache --zero-stats || true
     - ccache --show-stats || true
   after_script:
@@ -148,6 +149,11 @@ meson-clang:
     GALLIUM_DRIVERS: "auto"
     CC: "ccache clang-7"
     CXX: "ccache clang++-7"
+  before_script:
+    - export CCACHE_BASEDIR="$PWD" CCACHE_DIR="$PWD/ccache"
+    - ccache --zero-stats --show-stats || true
+     # clang++ breaks if it picks up the GCC 8 directory without libstdc++.so
+    - apt-get remove -y libgcc-8-dev
 
 meson-vulkan:
   extends: .meson-build

.gitlab-ci/debian-install.sh

@@ -21,6 +21,24 @@ echo 'deb https://deb.debian.org/debian stretch-backports main' >/etc/apt/source
 
 apt-get update
 apt-get install -y -t stretch-backports \
+      llvm-3.9-dev \
+      libclang-3.9-dev \
+      llvm-5.0-dev \
+      llvm-6.0-dev \
+      llvm-7-dev \
+      clang-5.0 \
+      libclang-5.0-dev \
+      clang-6.0 \
+      libclang-6.0-dev \
+      g++ \
+      clang-7 \
+      libclang-7-dev
+
+# Install remaining packages from Debian buster to get newer versions
+add-apt-repository "deb https://deb.debian.org/debian/ buster main"
+add-apt-repository "deb https://deb.debian.org/debian/ buster-updates main"
+apt-get update
+apt-get install -y \
       bzip2 \
       zlib1g-dev \
       pkg-config \
@@ -33,19 +51,7 @@ apt-get install -y -t stretch-backports \
       libxxf86vm-dev \
       libvdpau-dev \
       libva-dev \
-      llvm-3.9-dev \
-      libclang-3.9-dev \
-      llvm-5.0-dev \
-      llvm-6.0-dev \
-      llvm-7-dev \
-      clang-5.0 \
-      libclang-5.0-dev \
-      clang-6.0 \
-      libclang-6.0-dev \
-      g++ \
       gcc \
-      clang-7 \
-      libclang-7-dev \
       libclc-dev \
       libxvmc-dev \
       libomxil-bellagio-dev \
@@ -54,7 +60,7 @@ apt-get install -y -t stretch-backports \
       libx11-xcb-dev \
       x11proto-xf86vidmode-dev \
       libelf-dev \
-      libunwind8-dev \
+      libunwind-dev \
       libglvnd-dev \
       python-mako \
       python3-mako \