ci: add pre-build and post-build steps to Linux

The pre-build step will allow actions to be executed before the
CMake build but after Ninja and sccache have been downloaded, so
they can be used in the pre-build step. The env step is meant for
setting up environment variables anyway, rather than performing
actions.

The post-build step will allow extra artifacts to be computed after
the build is complete.

.gitlab/ci/post_build.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+
+set -e
+
+quietly() {
+  readonly log="/tmp/quietly-$RANDOM.log"
+  if ! "$@" >"$log" 2>&1; then
+    ret=$?
+    cat "$log"
+    rm -f "$log"
+    exit $ret
+  fi
+  rm -f "$log"
+}
+
+if test -r ".gitlab/ci/post_build_${CMAKE_CONFIGURATION}.sh"; then
+  source ".gitlab/ci/post_build_${CMAKE_CONFIGURATION}.sh"
+fi

.gitlab/ci/pre_build.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+
+set -e
+
+quietly() {
+  readonly log="/tmp/quietly-$RANDOM.log"
+  if ! "$@" >"$log" 2>&1; then
+    ret=$?
+    cat "$log"
+    rm -f "$log"
+    exit $ret
+  fi
+  rm -f "$log"
+}
+
+if test -r ".gitlab/ci/pre_build_${CMAKE_CONFIGURATION}.sh"; then
+  source ".gitlab/ci/pre_build_${CMAKE_CONFIGURATION}.sh"
+fi

.gitlab/os-linux.yml

@@ -465,8 +465,10 @@
         - .gitlab/ci/sccache.sh
         - sccache --start-server
         - sccache --show-stats
+        - .gitlab/ci/pre_build.sh
         - "$LAUNCHER ctest -VV -S .gitlab/ci/ctest_configure.cmake"
         - "$LAUNCHER ctest -VV -S .gitlab/ci/ctest_build.cmake"
+        - .gitlab/ci/post_build.sh
         - sccache --show-stats
 
     interruptible: true