net-libs/nodejs: filter out -flto from *FLAGS; -Ofast workarounds

[jelinekto]

net-libs/nodejs: There's lto USE flag that should be used to inject -flto instead, also LTO currently does not work with GCC 11 (you'll be asked to disable the USE flag when you try to emerge it).

app-editors/emacs: You'll be explicitly asked to disable -ffinite-math-only during emerge.

gui-apps/gammastep: Fork of x11-misc/redshift, -ffinite-math-only breaks it in the exactly same way.

[jelinekto]

I've added a (possibly) temporary workaround for Firefox; -Ofast and -ffast-math get filtered by flagomatic and specifying -fno-honor-infinities -fno-honor-nans -fno-math-errno -ffinite-math-only -fassociative-math -freciprocal-math -fno-signed-zeros -fno-trapping-math -ffp-contract=fast (aka the flags activated by Clang -ffast-math) causes the build to fail.

Obviously investigating Firefox build failures without a CPU that is beefy enough is an absolute bitch and would cause me to lose my will to live pretty fast, so I suggest falling back to -fno-trapping-math -fno-math-errno which makes it possible to at least build the package with both Clang and GCC for now. So far I can tell you removing -ffinite-math-only doesn't help.

[InBetweenNames]

Thank you!