More than 10 MLD degradation observed with RELEASE target

This issue can be reproduced with c7b43a06 and stv71MC48c(-10dB scaled version of stv71MC48c.wav input stream).

MLD observed with default build (in debug mode) : 0.002886

MLD observed in release mode : 11.564246

Steps to reproduce :

1. Build IVAS BASOP code with default Makefile (this uses -O0 compilation option, same as debug mode)
2. Run command : ./IVAS_rend -i scripts/testv/stv71MC48c.wav -if 7_1 -o 7_1_to_t_design_4None_20msNone.wav -of scripts/ls_layouts/t_design_4.txt -fs 48 -no_delay_cmp -q -fr 20
3. Build fixed point code by setting RELEASE=1 in Makefile
4. repeat step (2)
5. Capture MLD score for both streams w.r.t. floating point out renderer output.

Amplitude difference of up to 0.05 observed in some channels.

output in debug mode : 7_1_to_t_design_4None_20msNone

output in release mode :7_1_to_t_design_4None_20msNone