AlwaysBuild not honored when using ninja execution engine

[pmova7173630]

Describe the bug
The AlwaysBuild command for a target is not honored when using the experimental ninja execution engine.

Required information

• Link to SCons Users thread discussing your issue.
  https://discord.com/channels/571796279483564041/1521525108106330122/1521525112195780709

• Version of SCons
  Version 4.10.2, HEAD of master. However I know this goes back to the original ninja release.

• Version of Python
  Python 3.14.5, although I know it also fails on 3.6 and 3.10

• Which python distribution if applicable (python.org, cygwin, anaconda, macports, brew,etc)
  python.org

• How you installed SCons
  This happens both on using “scons-local” as well as from the source tree.

• What Platform are you on? (Linux/Windows and which version)
  Linux - Ubuntu 20.04, Ubuntu 24.04, Alpine 3.24.1

• How to reproduce your issue? Please include a small self contained reproducer. Likely a SConstruct should do for most issues.

Here is a simple sconstruct using test2.cpp from test/ninja/ninja-fixture

SetOption('experimental','ninja')
DefaultEnvironment(tools=[])
env = Environment()
env.Tool('ninja')

# Compile source to object
obj = env.Object('test2.cpp')
# Force rebuild of object file every time
env.AlwaysBuild(obj)

# Link object to executable
env.Program(target='always_build', source=obj)

• How you invoke scons (The command line you're using "scons --flags some_arguments”)

When using python3 <path_to_worktree>/scripts/scons.py it will build the app and then on subsequent calls will rebuild the .o file per the AlwaysBuild on the target.

When using python3 <path_to_worktree>/scripts/scons.py --experimental=ninja it will build the app and then on subsequent calls there is no work to do (which is wrong).