build: add libdex-1 requirement for libsysprof-profile

Being able to manage asynchronous operations with libdex will drastically
simplify how we implement the profiler and instruments. We may eventually
do the same with libsysprof-analyze to parallelize some operations.

org.gnome.Sysprof.Devel.json

@@ -98,6 +98,25 @@
                 }
             ]
         },
+        {
+            "name" : "libdex",
+            "buildsystem" : "meson",
+            "config-opts" : [
+                "--buildtype=debugoptimized",
+                "-Ddocs=false",
+                "-Dintrospection=enabled",
+                "-Dexamples=false",
+                "-Dtests=false",
+                "-Dsysprof=false"
+            ],
+            "sources" : [
+                {
+                    "type" : "git",
+                    "url" : "https://gitlab.gnome.org/chergert/libdex.git",
+                    "branch" : "main"
+                }
+            ]
+        },
         {
             "name" : "sysprof",
             "config-opts" : [