gitlab-ci: make needs explicitly empty where possible

In a pipeline with the `prep` stage, all `build` stage jobs without
an explicit `needs` list implicitly `needs` all `prep` job
artifacts. Make these explicitly empty so that the jobs can start
without waiting for and downloading the `prep` artifacts which are
then ignored anyways.

.gitlab-ci.yml

@@ -91,6 +91,7 @@ b:version-update:
     variables:
         CMAKE_CI_JOB_UPDATES_VERSION: "true"
         CMAKE_CI_JOB_NO_MR: "true"
+    needs: []
 
 # Documentation builds
 
@@ -120,6 +121,7 @@ l:spellcheck:
         - .cmake_spellcheck_linux
         - .linux_x86_64_tags
         - .rules
+    needs: []
 
 l:iwyu-debian13:
     extends:
@@ -128,6 +130,7 @@ l:iwyu-debian13:
         - .linux_x86_64_tags
         - .cmake_cdash_artifacts
         - .rules
+    needs: []
 
 l:tidy-fedora43:
     extends:
@@ -137,6 +140,7 @@ l:tidy-fedora43:
         - .linux_x86_64_tags
         - .cmake_cdash_artifacts
         - .rules
+    needs: []
 
 l:sphinx-fedora43:
     extends:
@@ -148,6 +152,7 @@ l:sphinx-fedora43:
     variables:
         CMAKE_CI_JOB_CONTINUOUS: "true"
         CMAKE_CI_JOB_HELP: "true"
+    needs: []
 
 l:clang-analyzer-fedora43:
     extends:
@@ -157,6 +162,7 @@ l:clang-analyzer-fedora43:
         - .rules
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
+    needs: []
 
 l:clang-fuzzing-fedora43:
     extends:
@@ -164,6 +170,7 @@ l:clang-fuzzing-fedora43:
         - .cmake_build_linux
         - .linux_x86_64_tags
         - .rules
+    needs: []
 
 l:clazy-fedora43:
     extends:
@@ -171,6 +178,7 @@ l:clazy-fedora43:
         - .cmake_build_linux
         - .linux_x86_64_tags
         - .rules
+    needs: []
 
 # Coverage builds
 
@@ -184,6 +192,7 @@ b:fedora43-gcc-gcov:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 t:fedora43-gcc-gcov:
     extends:
@@ -222,6 +231,7 @@ b:fedora43-bullseye-coverage:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_NO_MR: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 t:fedora43-bullseye-coverage:
     extends:
@@ -263,6 +273,7 @@ b:centos7-x86_64:
     variables:
         CMAKE_CI_ARTIFACTS_NAME: "artifacts-centos7-x86_64"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 b:centos8-aarch64:
     extends:
@@ -275,6 +286,7 @@ b:centos8-aarch64:
         CMAKE_CI_ARTIFACTS_NAME: "artifacts-centos8-aarch64"
         CMAKE_CI_JOB_NO_MR: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 t:debian13-ninja:
     extends:
@@ -688,6 +700,7 @@ b:fedora43-ninja:
     variables:
         CMAKE_CI_JOB_CONTINUOUS: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 b:fedora43-makefiles-symlinked:
     extends:
@@ -699,6 +712,7 @@ b:fedora43-makefiles-symlinked:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 b:debian13-makefiles-inplace:
     extends:
@@ -709,6 +723,7 @@ b:debian13-makefiles-inplace:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 b:debian13-extdeps:
     extends:
@@ -719,6 +734,7 @@ b:debian13-extdeps:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 b:debian13-aarch64-extdeps:
     extends:
@@ -729,6 +745,7 @@ b:debian13-aarch64-extdeps:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 b:fedora43-extdeps:
     extends:
@@ -739,6 +756,7 @@ b:fedora43-extdeps:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 t:fedora43-ninja:
     extends:
@@ -1110,6 +1128,7 @@ b:fedora43-asan:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 t:fedora43-asan:
     extends:
@@ -1148,6 +1167,7 @@ b:macos-x86_64-ninja:
     variables:
         CMAKE_CI_JOB_NO_MR: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 b:macos-arm64-ninja:
     extends:
@@ -1159,6 +1179,7 @@ b:macos-arm64-ninja:
     variables:
         CMAKE_CI_JOB_CONTINUOUS: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 b:macos-arm64-ninja-symlinked:
     extends:
@@ -1170,6 +1191,7 @@ b:macos-arm64-ninja-symlinked:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 b:macos-arm64-pch:
     extends:
@@ -1180,6 +1202,7 @@ b:macos-arm64-pch:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 t:macos-x86_64-ninja:
     extends:
@@ -1228,6 +1251,7 @@ b:macos-x86_64-makefiles:
         - .rules
     variables:
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 t:macos-x86_64-makefiles:
     extends:
@@ -1402,6 +1426,7 @@ b:windows-vs2026-x64-ninja:
     variables:
         CMAKE_CI_JOB_CONTINUOUS: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 b:windows-vs2026-x64-pch:
     extends:
@@ -1412,6 +1437,7 @@ b:windows-vs2026-x64-pch:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 t:windows-vs2026-x64-ninja:
     extends:
@@ -1704,6 +1730,7 @@ b:windows-arm64-vs2026-ninja:
     variables:
         CMAKE_CI_JOB_NIGHTLY: "true"
         CMAKE_CI_JOB_RUN_MANUALLY: "true"
+    needs: []
 
 t:windows-arm64-vs2026-ninja:
     extends: