Ignore MSVC in test.

Author: cjgillot

tests/codegen/debug-fndef-size.rs

@@ -1,5 +1,6 @@
 // Verify that `i32::cmp` FnDef type is declared with size 0 and align 1 in LLVM debuginfo.
 // compile-flags: -O -g -Cno-prepopulate-passes
+// ignore-msvc the types are mangled differently
 
 use std::cmp::Ordering;