Fix pester-tests relative file handling
Fix pester-tests relative file handling

- `APP_BASE` was made into an absolute path
- `%.ps1` target now runs without `--file` but instead with `&`
- ^ also cd's into pester-tests first

KarolKaczmarek/PowerShell,KarolKaczmarek/PowerShell,jsoref/PowerShell,TravisEz13/PowerShell,bingbing8/PowerShell,KarolKaczmarek/PowerShell,jsoref/PowerShell,kmosher/PowerShell,jsoref/PowerShell,bingbing8/PowerShell,jsoref/PowerShell,PaulHigin/PowerShell,bmanikm/PowerShell,JamesWTruher/PowerShell-1,daxian-dbw/PowerShell,KarolKaczmarek/PowerShell,daxian-dbw/PowerShell,jsoref/PowerShell,bmanikm/PowerShell,bmanikm/PowerShell,bingbing8/PowerShell,kmosher/PowerShell,bingbing8/PowerShell,PaulHigin/PowerShell,bingbing8/PowerShell,TravisEz13/PowerShell,JamesWTruher/PowerShell-1,daxian-dbw/PowerShell,KarolKaczmarek/PowerShell,bmanikm/PowerShell,JamesWTruher/PowerShell-1,TravisEz13/PowerShell,JamesWTruher/PowerShell-1,PaulHigin/PowerShell,kmosher/PowerShell,bmanikm/PowerShell,PaulHigin/PowerShell,daxian-dbw/PowerShell,kmosher/PowerShell,kmosher/PowerShell,TravisEz13/PowerShell