[lldb][test] Add test for no_unique_address when mixed with bitfields (…

…llvm#108155)

This is the root-cause for the LLDB failures that started occurring
after llvm#105865.

The DWARFASTParserClang has logic to try derive unnamed bitfields from
DWARF offsets. In this case we treat `padding` as a 1-byte size field
that would overlap with `flag`, and decide we need to introduce an
unnamed bitfield into the AST, which is incorrect.

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

@@ -0,0 +1,28 @@
+// LLDB currently erroneously adds an unnamed bitfield
+// into the AST when an overlapping no_unique_address
+// field precedes a bitfield.
+
+// RUN: %clang --target=x86_64-apple-macosx -c -gdwarf -o %t %s
+// RUN: %lldb %t \
+// RUN:   -o "target var global" \
+// RUN:   -o "image dump ast" \
+// RUN:   -o exit | FileCheck %s
+
+// CHECK:      (lldb) image dump ast
+// CHECK:      CXXRecordDecl {{.*}} struct Foo definition
+// CHECK:      |-FieldDecl {{.*}} data 'char[5]'
+// CHECK-NEXT: |-FieldDecl {{.*}} padding 'Empty'
+// CHECK-NEXT: |-FieldDecl {{.*}} 'int'
+// CHECK-NEXT: | `-IntegerLiteral {{.*}} 'int' 8
+// CHECK-NEXT: `-FieldDecl {{.*}} sloc> flag 'unsigned long'
+// CHECK-NEXT:   `-IntegerLiteral {{.*}} 'int' 1
+
+struct Empty {};
+
+struct Foo {
+  char data[5];
+  [[no_unique_address]] Empty padding;
+  unsigned long flag : 1;
+};
+
+Foo global;