Update ad4696_iio to use no-OS Makefile and debug build error

[pamolloy]

I noticed that the ad4696_iio project is the only one not using the no-OS Makefiles. When I tried updating the project Makefile I ran into the following:

[16:27:36]  Mbed-OS build completed
[16:28:18]  putting mbed-os object files names to text file
[16:28:18]  Linking srcs to created project
mkdir: missing operand
Try 'mkdir --help' for more information.
make[1]: [/home/runner/work/precision-converters-firmware/precision-converters-firmware/libs/no-OS/tools/scripts/generic.mk:421: update] Error 1 (ignored)
[16:28:18]  putting project build pre-requisite names to text files
[16:28:18] [LD] 
/home/runner/work/precision-converters-firmware/precision-converters-firmware/gcc-arm-none-eabi-10.3-2021.10/bin/../lib/gcc/arm-none-eabi/10.3.1/../../../../arm-none-eabi/bin/ld: /home/runner/work/precision-converters-firmware/precision-converters-firmware/libs/no-OS/libraries/mbed/BUILD/SDP_K1/GCC_ARM/mbed-os/platform/source/mbed_sdk_boot.o: in function `__wrap_main':
/home/runner/work/precision-converters-firmware/precision-converters-firmware/libs/no-OS/libraries/mbed/mbed-os/platform/source/mbed_sdk_boot.c:177: undefined reference to `main'
collect2: error: ld returned 1 exit status
make[1]: *** [/home/runner/work/precision-converters-firmware/precision-converters-firmware/libs/no-OS/tools/scripts/generic.mk:395: /home/runner/work/precision-converters-firmware/precision-converters-firmware/projects/ad4696_iio/build/ad4696_iio.elf] Error 1
make: *** [/home/runner/work/precision-converters-firmware/precision-converters-firmware/libs/no-OS/tools/scripts/generic.mk:333: all] Error 2

[mphalke]

@pamolloy We can fix this. We have moved to no-os based make scripts for this project on our internal BB repo but looks like missed to update this one on the github

[pamolloy]

This project still appears to have some issue since it is the only one that does not build due to the following:

[mbed] Working path "/home/runner/work/precision-converters-firmware/precision-converters-firmware/libraries/no-OS/libraries/mbed" (library)
[mbed] Program path "/home/runner/work/precision-converters-firmware/precision-converters-firmware/libraries/no-OS/libraries/mbed"
[20:42:07]  Mbed-OS build completed
[20:42:56]  putting mbed-os object files names to text file
[20:42:56] Linking srcs to created project
mkdir: missing operand
Try 'mkdir --help' for more information.
make[1]: *** [/home/runner/work/precision-converters-firmware/precision-converters-firmware/libraries/no-OS/tools/scripts/generic.mk:376: update] Error 1
make: *** [/home/runner/work/precision-converters-firmware/precision-converters-firmware/libraries/no-OS/tools/scripts/generic.mk:257: all] Error 2
Error: Process completed with exit code 2.

Once it is fixed it should be added to the Github workflow.