Github actions:

* Limit parallel builds to 4 in order to avoid hitting fetch rate limit on Ubuntu.
* Re-enable older Ubuntu builds.

Author: mikeov

.github/workflows/build.yml

@@ -14,6 +14,7 @@ jobs:
 
   linux-build-docker:
     strategy:
+      max-parallel: 4
       matrix:
         distro: [ubuntu, centos, rockylinux, amazonlinux, debian, i386/ubuntu]
         exclude:
@@ -48,42 +49,42 @@ jobs:
             btype: release
             buser: qfsbuild
             runs_on: ubuntu-latest
-          # - distro: ubuntu
-            # ver: 18.04
-            # codecov: no
-            # btype: release
-            # buser: qfsbuild
-            # runs_on: ubuntu-latest
-          # - distro: ubuntu
-            # ver: 18.04
-            # codecov: yes
-            # btype: release
-            # buser: qfsbuild
-            # runs_on: ubuntu-latest
-          # - distro: ubuntu
-            # ver: 18.04
-            # codecov: no
-            # btype: debug
-            # buser: qfsbuild
-            # runs_on: ubuntu-latest
-          # - distro: ubuntu
-            # ver: 18.04
-            # codecov: no
-            # btype: release
-            # buser: root
-            # runs_on: ubuntu-latest
-          # - distro: ubuntu
-            # ver: 16.04
-            # codecov: no
-            # btype: release
-            # buser: qfsbuild
-            # runs_on: ubuntu-latest
-          # - distro: ubuntu
-            # ver: 14.04
-            # codecov: no
-            # btype: release
-            # buser: qfsbuild
-            # runs_on: ubuntu-latest
+          - distro: ubuntu
+            ver: 18.04
+            codecov: no
+            btype: release
+            buser: qfsbuild
+            runs_on: ubuntu-latest
+          - distro: ubuntu
+            ver: 18.04
+            codecov: yes
+            btype: release
+            buser: qfsbuild
+            runs_on: ubuntu-latest
+          - distro: ubuntu
+            ver: 18.04
+            codecov: no
+            btype: debug
+            buser: qfsbuild
+            runs_on: ubuntu-latest
+          - distro: ubuntu
+            ver: 18.04
+            codecov: no
+            btype: release
+            buser: root
+            runs_on: ubuntu-latest
+          - distro: ubuntu
+            ver: 16.04
+            codecov: no
+            btype: release
+            buser: qfsbuild
+            runs_on: ubuntu-latest
+          - distro: ubuntu
+            ver: 14.04
+            codecov: no
+            btype: release
+            buser: qfsbuild
+            runs_on: ubuntu-latest
           - distro: debian
             ver: 12
             codecov: no