GHA: tidy up parallel options, improve performance for some jobs

- replace `--parallel <n>` and `-j<n>` for individual commands with
  `MAKEFLAGS`, for jobs not yet doing it.
  This enables parallel builds in distcheck / maketgz-and-verify-in-tree,
  where `-j` option was missing.
- add `--parallel` for iOS Xcode job for improved performance.
- drop redundant `-j5` for Android jobs.
- drop stray `cmake --config` options from single-target jobs (cygwin,
  msys/mingw, dl-mingw, non-native). Drop redundant
  `CMAKE_RUNTIME_OUTPUT_DIRECTORY_*` settings too.
- GHA/windows: add timeout for package install steps where missing.
- GHA/non-native: specify target type explicitly for iOS cmake jobs.
  Xcode default was already Debug, single-target default was generic,
  now it's Release, with unity batch to keep it fast.

`MAKEFLAGS` is necessary for autotools jobs and CMake jobs using
the default (GNU Make) generator. It's ignored by Ninja and other tools.
`cmake --parallel` is still necessary for jobs with Visual Studio or
Xcode generators. Parallelism is 5 for GHA Linux and Windows runners,
4 for macOS, 3 for VMs, 2 for AppVeyor.

Closes #16502

.github/workflows/macos.yml

@@ -47,8 +47,8 @@ permissions: {}
 # newer than the 10.8 required by `CFURLCreateDataAndPropertiesFromResource`.
 
 env:
-  LDFLAGS: -w  # suppress 'object file was built for newer macOS version than being linked' warnings
   MAKEFLAGS: -j 4
+  LDFLAGS: -w  # suppress 'object file was built for newer macOS version than being linked' warnings
 
 jobs:
   macos: