linker: Report linker flavors incompatible with the current target

Previously they would be reported as link time errors about unknown linker options

compiler/rustc_target/src/lib.rs

@@ -11,6 +11,7 @@
 #![feature(assert_matches)]
 #![feature(associated_type_bounds)]
 #![feature(exhaustive_patterns)]
+#![feature(iter_intersperse)]
 #![feature(min_specialization)]
 #![feature(never_type)]
 #![feature(rustc_attrs)]