remove duplicate symbols for real gcc10 compatibility

[DvirDukhan]

This PR adds -fcommon to gcc compile flag, to avoid errors on multiple definitions of the same variable.
see https://gcc.gnu.org/gcc-10/porting_to.html
however, this is just a workaround and we should have a proper, in-depth solution

[codecov]

Codecov Report

Merging #825 (ff9482b) into master (8e40eaf) will increase coverage by 0.04%.
The diff coverage is 93.75%.

❗ Current head ff9482b differs from pull request most recent head aadc5e9. Consider uploading reports for the commit aadc5e9 to get more accurate results

@@            Coverage Diff             @@
##           master     #825      +/-   ##
==========================================
+ Coverage   79.91%   79.96%   +0.04%     
==========================================
  Files          53       53              
  Lines        8044     8019      -25     
==========================================
- Hits         6428     6412      -16     
+ Misses       1616     1607       -9     

Impacted Files	Coverage Δ
src/execution/DAG/dag.c	91.73% <88.88%> (+1.47%)	⬆️
src/redisai.c	86.99% <95.23%> (+1.07%)	⬆️
src/execution/parsing/dag_parser.c	96.01% <100.00%> (+0.01%)	⬆️
src/execution/parsing/deprecated.c	79.70% <100.00%> (-1.69%)	⬇️
...ckends/libtorch_c/torch_extensions/torch_redis.cpp	94.73% <0.00%> (-0.22%)	⬇️
src/backends/libtorch_c/torch_c.cpp	63.94% <0.00%> (-0.18%)	⬇️
src/backends/torch.c	84.19% <0.00%> (-0.06%)	⬇️

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