openswan: Restore -fPIE to USERCOMPILE flags

The default USERCOMPILE variable uses -fPIE so we bring this back.
This also fixes linking problems for MIPS when non-PIC objects
are used to form a PIC one.

Fixes the following linking problem on MIPS:
connections.o: relocation R_MIPS_HI16 against `__gnu_local_gp'
can not be used when making a shared object; recompile with -fPIC

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>