Build problem under Arch Linux #90

What steps will reproduce the problem?
1. Build textroom stable version or from svn using gcc 4.7.0, autoconf 2.69.
2. get error messages like me or User eigengrau 
(https://aur.archlinux.org/packages.php?ID=31597)
> sxfile/getusername.cpp: In function 'QString currentUserNameUnix()':
> sxfile/getusername.cpp:35:38: error: 'geteuid' was not declared in this scope 

What is the expected output? What do you see instead?
expected it to build, but it does not.

What version of the product are you using? On what operating system?
both 0.8.2 and svn are affected.

Please provide any additional information below.
having the following sed-command in my build scriptlet fixes the issue.
> sed -i '19i#include <unistd.h>' library/sxfile/getusername.cpp