Use new targets option for docs

rust-lang/docs.rs#343 (comment)

Author: rubberduck203

Cargo.toml

@@ -18,10 +18,8 @@ exclude = [
 maintenance = { status = "actively-developed" }
 
 [package.metadata.docs.rs]
-# thumbv7m-none-eabi is not a supported target on docs.rs,
-# however the target is not relevant for docs.
-# https://github.com/stm32-rs/stm32f3xx-hal/issues/46
-default-target = "x86_64-unknown-linux-gnu"
+default-target = "thumbv7em-none-eabihf"
+targets = [] # build only default target for docs
 
 [dependencies]
 cortex-m = "0.6.2"