No you should not edit any subdir.mk file: it will be overwritten next time you build the project...
The reason you have this is that, for some reason, someone decided to set specific build settings for this folder. In the project explorer this folder should appear with a little pin on its top right corner.
The right way to go is to right click on the folder that causes the problem then select Properties and look at build settings to see if there is something that is really needed;
- If this is true you should edit the Compiler settings to select the hard FPU ABI.
- If there is no specific setting needed, you can close the properties dialog then right-click again on the folder and select Resource configurations... >> Reset to default. Then you will be proposed with all subdirectories that set folder specific options: just select the ones that should not and click reset; then your problem should be resolved.
Of course look at all your folders to see if there are other “pinned” folders...
Hope this helps,