Add -fcommon to CFLAGS for GCC 10+ compatibility

[Luyoung0001]

Summary

This change adds the -fcommon flag to our build configuration to maintain compatibility with GCC version 10 and above. The newer versions of GCC default to -fno-common, which leads to multiple definition errors for projects that relied on the older -fcommon behavior.

Details

• GCC 10 and later versions have changed the default setting from -fcommon to -fno-common. This affects the handling of multiple definitions of the same global variable across different files, which previously were silently merged but now cause build errors.
• By explicitly setting -fcommon in our build scripts, we ensure that our code will continue to compile without errors across all supported versions of GCC.
• This is particularly important for legacy codebases or projects with multiple definitions of the same variables across different files.

Impact

• Ensures build stability and backward compatibility with older GCC versions.
• Prevents multiple definition errors during the linking phase when using GCC 10 or newer.

Please review the changes and merge if everything is in order. Feedback is welcome!