Add migration guide for #9718 (#10578)

[cabal.git] / Cabal-tests / tests / ParserTests / regressions / cc-options-with-optimization.check

[option-opt-c] 'cc-options: -O[n]' is generally not needed. When building with  optimisations Cabal automatically adds '-O2' for C code. Setting it yourself interferes with the --disable-optimization flag.