ci: Convert Fedora+Ninja-Multi-Config job to common conventions

Drop its former one-off infrastructure.

.gitlab-ci.yml

@@ -339,6 +339,14 @@ t:fedora43-ninja-lfortran:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
 
+t:fedora43-ninja-multi:
+    extends:
+        - .fedora43_ninja_multi
+        - .cmake_test_linux_release
+        - .linux_x86_64_tags
+        - .run_dependent
+        - .needs_centos7_x86_64
+
 t:fedora43-ninja-clang:
     extends:
         - .fedora43_ninja_clang
@@ -707,16 +715,6 @@ t:fedora43-makefiles-symlinked:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
 
-t:fedora43-ninja-multi:
-    extends:
-        - .fedora43_ninja_multi
-        - .cmake_test_linux_external
-        - .linux_x86_64_tags
-        - .cmake_junit_artifacts
-        - .run_dependent
-    needs:
-        - t:fedora43-ninja
-
 t:intel2016u2-makefiles:
     extends:
         - .cmake_test_linux_intelclassic_makefiles

.gitlab/os-linux.yml

@@ -235,14 +235,6 @@
         CMAKE_CI_BUILD_TYPE: Release
         CTEST_NO_WARNINGS_ALLOWED: 1
 
-.fedora43_ninja_multi:
-    extends: .fedora43
-
-    variables:
-        CMAKE_CONFIGURATION: fedora43_ninja_multi
-        CTEST_NO_WARNINGS_ALLOWED: 1
-        CMAKE_GENERATOR: "Ninja Multi-Config"
-
 .fedora43_makefiles:
     extends: .fedora43
 
@@ -310,6 +302,13 @@
         CMAKE_CONFIGURATION: fedora43_ninja_lfortran
         CTEST_LABELS: "Fortran"
 
+.fedora43_ninja_multi:
+    extends: .fedora43
+
+    variables:
+        CMAKE_CONFIGURATION: fedora43_ninja_multi
+        CMAKE_GENERATOR: "Ninja Multi-Config"
+
 .fedora43_ninja_clang:
     extends: .fedora43
 
@@ -883,19 +882,6 @@
 
     interruptible: true
 
-.cmake_test_linux_external:
-    stage: test-ext
-
-    script:
-        - *before_script_linux
-        - .gitlab/ci/sccache.sh
-        - sccache --start-server
-        - sccache --show-stats
-        - "$LAUNCHER build/install/bin/ctest --output-on-failure -V -S .gitlab/ci/ctest_standalone.cmake"
-        - sccache --show-stats
-
-    interruptible: true
-
 .cmake_test_linux_intelclassic_makefiles:
     extends:
         - .intelclassic_makefiles