just: refactor macOS build script

Builds still intermittently fail a lot for me. So let's retry the
build once before giving up.

To avoid repetition we use a shell for loop.

Justfile

@@ -39,14 +39,11 @@ release-build-macos tag:
 
   rm -rf build dist
   git checkout {{tag}}
-  ./build-macos.py --python cpython-3.8 --optimizations pgo
-  ./build-macos.py --python cpython-3.8 --optimizations pgo+lto
-  ./build-macos.py --python cpython-3.9 --optimizations pgo
-  ./build-macos.py --python cpython-3.9 --optimizations pgo+lto
-  ./build-macos.py --python cpython-3.10 --optimizations pgo
-  ./build-macos.py --python cpython-3.10 --optimizations pgo+lto
-  ./build-macos.py --python cpython-3.11 --optimizations pgo
-  ./build-macos.py --python cpython-3.11 --optimizations pgo+lto
+  for py in cpython-3.8 cpython-3.9 cpython-3.10 cpython-3.11; do
+    for opt in pgo pgo+lto; do
+      ./build-macos.py --python $py --optimizations $opt || ./build-macos.py --python $py --optimizations $opt
+    done
+  done
 
 # Trigger builds of aarch64-apple-darwin release artifacts.
 release-build-macos-remote tag: