Two compilation fixes
- Fix parallel make, the same temp file name was used twice
cp: cannot stat 'xgen-getc': No such file or directory
- Fix dbus interface file not found when using a custom install prefix
gmake[2]: *** No rule to make target '/usr/share/dbus-1/interfaces/com.google.code.AccountsSSO.SingleSignOn.AuthService.xml', needed by 'sso-auth-service-gen.c'. Stop.