Replace get_mut(& with entry( for powerpc64le-unknown-freebsd

Author: pkubaj

compiler/rustc_target/src/spec/powerpc64le_unknown_freebsd.rs

@@ -3,7 +3,7 @@ use crate::spec::{LinkerFlavor, Target, TargetOptions};
 pub fn target() -> Target {
     let mut base = super::freebsd_base::opts();
     base.cpu = "ppc64le".to_string();
-    base.pre_link_args.get_mut(&LinkerFlavor::Gcc).or_default().push("-m64".to_string());
+    base.pre_link_args.entry(LinkerFlavor::Gcc).or_default().push("-m64".to_string());
     base.max_atomic_width = Some(64);
 
     Target {