Github CI/CD: checkout@v4, macos matrix updates

- Per Github messages, upgrade checkout@v3 to checkout@v4 due to an
  upgrade to Node.js.

- macos-11 is now a defunct image runner. Homebrew packages either have
  to compile from source or no longer install correctly.

- Update the macos compile matrix. Set CPACK_SUFFIX environment variable
  to indicate macOS hardware platform: macos-14 is M1, whereas macos-12
  and macos-13 are x86_64.

- Added notes with respect to the matrix.strategy runner images. The
  makefile builds use "-latest" because they don't produce artifacts,
  while (*) the CMake builds enumerate the images for which artifacts (+)
  are produced and the runner image's name is part of the artifact.

(*) "Whilst" for the rest of the Anglosphere.
(+) "Artefact" for the rest of the Anglosphere.

.github/workflows/build.yml

@@ -19,11 +19,16 @@ jobs:
   makefile:
     runs-on: ${{ matrix.os }}
     strategy:
+      #-
+      # The makefile builds DO NOT produce artifacts (*). Using the "-latest"
+      # runner images is sufficient.
+      #
+      # (*) "artefact" for the rest of the Anglosphere
+      #-
+
       matrix:
-        ## macos-10.15: Runner seems to be officially disabled, results in canceled
-        ## builds. Leaving this "as-is".
-        ##
-        os: [macos-12, ubuntu-20.04]
+        os: [macos-latest, ubuntu-latest]
+
         simulators:
           # These are supposed to match ALL in makefile.
           # Each job builds ~15 simulators.
@@ -34,7 +39,7 @@ jobs:
           - besm6 imlac tt2500 microvax3900 microvax1 rtvax1000 vaxstation3100m76 vaxstation4000m60
           - scelbi 3b2 i701 i704 i7010 i7070 i7080 i7090 sigma uc15 i650 sel32 intel-mds ibm1130
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       ## Workaround for remnant symlinks in /usr/local pointing back to
       ## macOS frameworks.
       ##