That will just makes it worse. What you want is a generic build but, straight from gcc...

There is no -march=generic option because -march indicates the instruction set the compiler can use,
and there is no generic instruction set applicable to all processors.

There is just too much that is different between AMD and Intel processors.

Edit: If you're only compiling for that one PC you can specify -march for that CPU.

https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html

Edit2: It might also be useful to mention what CPUs are inolved. If the AMD newer than Piledriver -march-core2 should work.
I have had no success with Piledriver and older.