scripts: gen_relocate_app: Use linker provided size variable.
scripts: gen_relocate_app: Use linker provided size variable.

This seems to solve the issue with GH-12033. There seems to be
some compiler optimization that was causing this issue. This
occurs only when the build is re-run by invoking cmake without
clearing the previous build.

Fixes:GH-12033

Signed-off-by: Adithya Baglody <06b44f6fa9a97a2b955c2d2cd070279967447860@intel.com>

galak/zephyr,nashif/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,punitvara/zephyr,Vudentz/zephyr,finikorg/zephyr,punitvara/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,Vudentz/zephyr,punitvara/zephyr,punitvara/zephyr,ldts/zephyr,galak/zephyr,finikorg/zephyr,galak/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,explora26/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,explora26/zephyr,finikorg/zephyr,punitvara/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,finikorg/zephyr,ldts/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,ldts/zephyr,Vudentz/zephyr,nashif/zephyr