Add possibility to match on both full target and components

Author: GuillaumeGomez

text/0000-cfg-target.md

@@ -1,6 +1,6 @@
 - Feature Name: `cfg-target`
 - Start Date: 2020-09-27
-- RFC PR: [rust-lang/rfcs#2991](https://github.com/rust-lang/rfcs/pull/2991)
+- RFC PR: [rust-lang/rfcs#3239](https://github.com/rust-lang/rfcs/pull/3239)
 - Rust Issue: [rust-lang/rust#0000](https://github.com/rust-lang/rust/issues/0000)
 
 # Summary
@@ -36,6 +36,16 @@ mod mac_catalyst;
 
 This includes `#[cfg_attr(target = "...", attr)]`.
 
+It would also support to specify each `target_*` inside a new `target`
+attribute as follows:
+
+```rust
+// So we can for example rewrite:
+#[cfg(all(target_os = "linux", target_arch = "arm"))]
+// as:
+#[cfg(target(os = "linux", arch = "arm"))]
+```
+
 # Reference-level explanation
 [reference-level-explanation]: #reference-level-explanation