Add execute bit back to build.py

[snnn]

Description:

It got removed in #5778. But the Android pipeline needs it.

Motivation and Context

• Why is this change required? What problem does it solve?
• If it fixes an open issue, please link to the issue here.

[guoyu-wang]

Do you think it's better we add 'python3' in front of the current CI definition? So this won't get affected by this kind of accidental change?

• script: python3 tools/ci_build/build.py --android --build_dir build --android_sdk ...

[snnn]

Do you think it's better we add 'python3' in front of the current CI definition? So this won't get affected by this kind of accidental change?

I feel either is fine. You can decide it.

[skottmckay]

Do you think it's better we add 'python3' in front of the current CI definition? So this won't get affected by this kind of accidental change?

I feel either is fine. You can decide it.

Given this has happened twice recently, adding python3 is probably better long term.

It happened to me on Windows and I didn't make any direct or intentional changes to the permissions for build.py (and given it was Windows it wasn't even obvious it had changed).

[guoyu-wang]

Do you think it's better we add 'python3' in front of the current CI definition? So this won't get affected by this kind of accidental change?

I feel either is fine. You can decide it.

Given this has happened twice recently, adding python3 is probably better long term.

It happened to me on Windows and I didn't make any direct or intentional changes to the permissions for build.py (and given it was Windows it wasn't even obvious it had changed).

This #5889 has the change to add python3 to CI command, it was trying to fix another unrelated Android CI failure