[lldb][test] Fixed the test no_unique_address-with-bitfields

Fixed the error `unable to create target: 'No available targets are compatible with triple "x86_64-apple-macosx10.4.0"'`.

Author: slydiman

lldb/test/Shell/SymbolFile/DWARF/no_unique_address-with-bitfields.cpp

@@ -8,6 +8,8 @@
 // RUN:   -o "image dump ast" \
 // RUN:   -o exit | FileCheck %s
 
+// REQUIRES: system-darwin
+
 // CHECK:      (lldb) image dump ast
 // CHECK:      CXXRecordDecl {{.*}} struct Foo definition
 // CHECK:      |-FieldDecl {{.*}} data 'char[5]'