Fix warnings specific to GCC 9.4

GCC 9.4 throws relocation errors when linking with -pie unless all objects are compiled with -fpie.
To resolve this, replaced -pie with -fpie to ensure consistent position-independent code generation
during both compilation and linking.

Signed-off-by: Yuvaraj Venkatesh <yuvaraj.venkatesh@arm.com>
Change-Id: Idc4402b904e9c66f2b43771eb0140ed049b1c0f5