BII android proot compatibility

[rakslice]

A BII build without JIT in ubuntu 20 04 armhf port running on android 9 pie via Termux proot-distro fails to launch, giving errors on pthread_create of threads (60hz thread, ethernet thread). In this scenario the pthread functionality available is limited to what is exposed by the android host system, which may be relevant.

One of the error messages is missing a newline.

It seems that if the pthread attr settings BII requests aren't compatible with the permissions situation, creating the thread just fails.

Disabling the geteuid() == 0 case in Set_pthread_attr() makes the problem go away -- separately from whatever pthread limitations we have from android, we also have the limitations of only regular user permissions despite running with apparent user geteuid() == 0

[rakslice]

There isn't any way to tell what pthread attr values are going to cause a problem for the pthread_create ahead of time AFAICT. The calls to set the values aren't reporting any errors.

[rakslice]

• We could in the case of euid 0 detect whether proot is present and if so not use attributes, because we probably aren't really root.
• We could just always retry thread creation without attributes if thread creation fails in the case where we use attributes.

[rakslice]

I implemented that first solution of detecting proot in https://github.com/rakslice/macemu/commits/proot_fix