[gdb-remote] process properly effective uid

Summary:
Someone wrote SetEffectiveSetEffectiveGroupID instead of SetEffectiveUserID.

After this fix, the android process list can show user names, e.g.

```
PID    PARENT USER       GROUP      EFF USER   EFF GROUP  TRIPLE                               ARGUMENTS
====== ====== ========== ========== ========== ========== ============================== ============================
529    1      root       0          root       0                                         /sbin/ueventd
```
Reviewers: labath,clayborg,aadsm,xiaobai

Subscribers:

llvm-svn: 373953