[GR-29808] Build jars first and then native images to minimize the used memory

Author: eregon

.github/workflows/ci.yml

@@ -95,7 +95,12 @@ jobs:
 
       - uses: ./build/.github/actions/setup-jvmci-graal
 
-      - name: Build TruffleRuby
+      # [GR-29808] We build everything except native images first,
+      # so that we minimize the memory used by mx, etc when building native images.
+      - name: Build TruffleRuby (jars)
+        run: jt build --env native --native-images=none
+      - run: free -m
+      - name: Build TruffleRuby (native images)
         run: jt build --env native
 
       - name: Create archive