package/ci: add dependencies between CircleCI jobs to limit credit usage.

Take the linux-gl, linux-vulkan and linux-nondeprecated builds as the
main sanity checks. If they pass, then the rest gets scheduled as well,
with further dependencies between them (such as WebGL2 tests being run
only if GLES3 passes).

Otherwise it often happens that until I'm able to push a fix for GCC
4.8 or an ES2-specific build failure, it already consumes 10 minutes on
15 jobs, which is quite a lot, especially for the macOS jobs.

package/ci/circleci.yml

@@ -614,23 +614,72 @@ jobs:
 workflows:
   version: 2
   build:
+    # While there's no actual execution or data dependency between the jobs,
+    # this is done in order to reduce unnecessary credit usage. The GL, Vulkan
+    # and non-deprecated Linux builds are taken as the main sanity checks. Only
+    # if they pass, the rest of the jobs gets gradually executed, with further
+    # dependencies especially for the macOS jobs that take the most credits.
     jobs:
     - linux-gl
-    - linux-arm64
+    - linux-arm64:
+        requires:
+        - linux-gl
+        - linux-vulkan
     - linux-vulkan
-    - linux-gles2
-    - linux-gles3
-    - linux-static
+    - linux-gles2:
+        requires:
+        - linux-gl
+    - linux-gles3:
+        requires:
+        - linux-gl
+    - linux-static:
+        requires:
+        - linux-gl
+        - linux-vulkan
     - linux-nondeprecated
-    - linux-sanitizers
-    - linux-threadsanitizer
-    - macos-gl
-    - macos-vulkan
-    - macos-gles3
-    - macos-static
-    - emscripten-webgl1
-    - emscripten-webgl2
-    - android-x86-gles2
-    - android-x86-gles3
-    - android-x86-vulkan
-    - ios-gles3
+    - linux-sanitizers:
+        requires:
+        - linux-gl
+    - linux-threadsanitizer:
+        requires:
+        - linux-sanitizers
+    - macos-gl:
+        requires:
+        - linux-gl
+        - linux-nondeprecated
+    - macos-vulkan:
+        requires:
+        - linux-vulkan
+        - macos-gl
+    - macos-gles3:
+        requires:
+        - linux-gles3
+        - macos-gl
+    - macos-static:
+        requires:
+        - linux-static
+        - macos-gl
+    - emscripten-webgl1:
+        requires:
+        - linux-gles2
+        - linux-static
+    - emscripten-webgl2:
+        requires:
+        - linux-gles3
+        - linux-static
+    - android-x86-gles2:
+        requires:
+        - linux-gles2
+        - linux-static
+    - android-x86-gles3:
+        requires:
+        - linux-gles3
+        - linux-static
+    - android-x86-vulkan:
+        requires:
+        - linux-vulkan
+        - linux-static
+    - ios-gles3:
+        requires:
+        - macos-gles3
+        - macos-static