Rollup merge of #40431 - fsasm:master, r=BurntSushi
Rollup merge of #40431 - fsasm:master, r=BurntSushi

rustc: Whitelist the FMA target feature

This commit adds the entry `"fma\0"` to the whitelist for the x86
target. LLVM already supports fma but rustc did not directly. Previously
rustc permitted `+fma` in the target-feature argument and enabled the use
of FMA instructions, but it did not list it in the configuration and
attributes.

fixes #40406

GBGamer/rust,graydon/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,GBGamer/rust,aidancully/rust,aidancully/rust