Ignore some mir-opt tests because GCC backend does not support unwinding from inline asm

tests/mir-opt/inline/asm_unwind.rs

@@ -4,6 +4,7 @@
 //@ needs-asm-support
 //@ needs-unwind
 //@ compile-flags: -Zinline-mir-hint-threshold=1000 -C debuginfo=full
+//@ ignore-backends: gcc
 #![feature(asm_unwind)]
 
 struct D;

tests/mir-opt/inline/inline_compatibility.rs

@@ -1,6 +1,7 @@
 // Checks that only functions with compatible attributes are inlined.
 //@ only-x86_64
 //@ compile-flags: -Cpanic=abort
+//@ ignore-backends: gcc
 
 #![crate_type = "lib"]
 #![feature(sanitize)]