You may want to add some commands to your GCC flag settings.
No problem, Eclipse can allow you this.
Right click on your project > Properties > C/C++ Build > Settings > Tool Settings > GCC C++ Compiler > Miscellaneous.
On the right, there is an input with the name Other flags.
Enter your command there.
For example, if when you compiling you have this error:
You can add this command to remove it:
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