rustc_target: Rename some target options to avoid tautology

`target.target_endian` -> `target.endian`
`target.target_c_int_width` -> `target.c_int_width`
`target.target_os` -> `target.os`
`target.target_env` -> `target.env`
`target.target_vendor` -> `target.vendor`
`target.target_family` -> `target.os_family`
`target.target_mcount` -> `target.mcount`

compiler/rustc_target/src/spec/powerpc_unknown_netbsd.rs

@@ -11,8 +11,8 @@ pub fn target() -> Target {
         data_layout: "E-m:e-p:32:32-i64:64-n32".to_string(),
         arch: "powerpc".to_string(),
         options: TargetOptions {
-            target_endian: "big".to_string(),
-            target_mcount: "__mcount".to_string(),
+            endian: "big".to_string(),
+            mcount: "__mcount".to_string(),
             ..base
         },
     }