ci: Introduce SanityCheck task that other tasks depend on

To avoid unnecessarily spinning up a lot of VMs / containers for entirely
broken commits, have a minimal task that all others depend on.

The concrete motivation for the change is to use sanitizers in the linux
tasks. As that makes the tests slower, the start of the CompilerWarnings would
be delayed even more. With this change the CompilerWarnings only depends on
the SanityCheck task.

This has the added advantage that now the CompilerWarnings task is not
prevented from running by (most) test failures (particularly annoying when
caused by a test that is flappy in HEAD).

Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Discussion: https://postgr.es/m/20221002205201.injtofbx4ax4erww@awork3.anarazel.de

.cirrus.yml

@@ -55,6 +55,78 @@ on_failure_meson: &on_failure_meson
     type: text/plain
 
 
+# To avoid unnecessarily spinning up a lot of VMs / containers for entirely
+# broken commits, have a minimal task that all others depend on.
+task:
+  name: SanityCheck
+
+  # If a specific OS is requested, don't run the sanity check. This shortens
+  # push-wait-for-ci cycle time a bit when debugging operating system specific
+  # failures. Uses skip instead of only_if, as cirrus otherwise warns about
+  # only_if conditions not matching.
+  skip: $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:.*'
+
+  env:
+    CPUS: 4
+    BUILD_JOBS: 8
+    TEST_JOBS: 8
+    CCACHE_DIR: ${CIRRUS_WORKING_DIR}/ccache_dir
+    # no options enabled, should be small
+    CCACHE_MAXSIZE: "150M"
+
+  # Container starts up quickly, but is slower at runtime, particularly for
+  # tests. Good for the briefly running sanity check.
+  container:
+    image: $CONTAINER_REPO/linux_debian_bullseye_ci:latest
+    cpu: $CPUS
+
+  ccache_cache:
+    folder: $CCACHE_DIR
+
+  create_user_script: |
+    useradd -m postgres
+    chown -R postgres:postgres .
+    mkdir -p ${CCACHE_DIR}
+    chown -R postgres:postgres ${CCACHE_DIR}
+    echo '* - memlock 134217728' > /etc/security/limits.d/postgres.conf
+    su postgres -c "ulimit -l -H && ulimit -l -S"
+    # Can't change container's kernel.core_pattern. Postgres user can't write
+    # to / normally. Change that.
+    chown root:postgres /
+    chmod g+rwx /
+
+  configure_script: |
+    su postgres <<-EOF
+      meson setup \
+        --buildtype=debug \
+        --auto-features=disabled \
+        -Dtap_tests=enabled \
+        build
+    EOF
+  build_script: |
+    su postgres <<-EOF
+      ninja -C build -j${BUILD_JOBS}
+    EOF
+  upload_caches: ccache
+
+  # Run a minimal set of tests. The main regression tests take too long for
+  # this purpose. For now this is a random quick pg_regress style test, and a
+  # tap test that exercises both a frontend binary and the backend.
+  test_minimal_script: |
+    su postgres <<-EOF
+      ulimit -c unlimited
+      meson test $MTEST_ARGS --num-processes ${TEST_JOBS} \
+        tmp_install cube/regress pg_ctl/001_start_stop
+    EOF
+
+  on_failure:
+    <<: *on_failure_meson
+    cores_script: |
+      mkdir -m 770 /tmp/cores
+      find / -maxdepth 1 -type f -name 'core*' -exec mv '{}' /tmp/cores/ \;
+      src/tools/ci/cores_backtrace.sh linux /tmp/cores
+
+
 task:
   name: FreeBSD - 13 - Meson
 
@@ -69,6 +141,7 @@ task:
     CPPFLAGS: -DRELCACHE_FORCE_RELEASE -DCOPY_PARSE_PLAN_TREES -DWRITE_READ_PARSE_PLAN_TREES -DRAW_EXPRESSION_COVERAGE_TEST
     CFLAGS: -Og -ggdb
 
+  depends_on: SanityCheck
   only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*freebsd.*'
 
   compute_engine_instance:
@@ -170,6 +243,7 @@ task:
     LINUX_CONFIGURE_FEATURES: *LINUX_CONFIGURE_FEATURES
     LINUX_MESON_FEATURES: *LINUX_MESON_FEATURES
 
+  depends_on: SanityCheck
   only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*linux.*'
 
   compute_engine_instance:
@@ -311,6 +385,7 @@ task:
     CFLAGS: -Og -ggdb
     CXXFLAGS: -Og -ggdb
 
+  depends_on: SanityCheck
   only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*(macos|darwin|osx).*'
 
   osx_instance:
@@ -430,6 +505,7 @@ task:
     # 0x8001 is SEM_FAILCRITICALERRORS | SEM_NOOPENFILEERRORBOX
     CIRRUS_WINDOWS_ERROR_MODE: 0x8001
 
+  depends_on: SanityCheck
   only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*windows.*'
 
   windows_container:
@@ -469,6 +545,8 @@ task:
   # worth using only_if despite being manual, otherwise this task will show up
   # when e.g. ci-os-only: linux is used.
   only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*mingw.*'
+  # otherwise it'll be sorted before other tasks
+  depends_on: SanityCheck
 
   windows_container:
     image: $CONTAINER_REPO/windows_ci_mingw64:latest
@@ -523,9 +601,12 @@ task:
 task:
   name: CompilerWarnings
 
-  # To limit unnecessary work only run this once the normal linux test succeeds
-  depends_on:
-    - Linux - Debian Bullseye - Meson
+  # To limit unnecessary work only run this once the SanityCheck
+  # succeeds. This is particularly important for this task as we intentionally
+  # use always: to continue after failures. Task that did not run count as a
+  # success, so we need to recheck SanityChecks's condition here ...
+  depends_on: SanityCheck
+  only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*'
 
   env:
     CPUS: 4
@@ -539,10 +620,6 @@ task:
     LINUX_CONFIGURE_FEATURES: *LINUX_CONFIGURE_FEATURES
     LINUX_MESON_FEATURES: *LINUX_MESON_FEATURES
 
-  # task that did not run, count as a success, so we need to recheck Linux'
-  # condition here ...
-  only_if: $CIRRUS_CHANGE_MESSAGE !=~ '.*\nci-os-only:.*' || $CIRRUS_CHANGE_MESSAGE =~ '.*\nci-os-only:[^\n]*linux.*'
-
   container:
     image: $CONTAINER_REPO/linux_debian_bullseye_ci:latest
     cpu: $CPUS