[CMake] Emit LLDB.framework.dSYM to avoid potential name collision with driver's lldb.dSYM

Summary:
Emit framework's dSYM bundle as LLDB.framework.dSYM instead of LLDB.dSYM, because the latter could conflict with the driver's lldb.dSYM when emitted in the same directory on case-insensitive file systems.
Requires https://reviews.llvm.org/D60862

Reviewers: friss, beanz, bogner

Subscribers: mgorny, lldb-commits, #lldb

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D60863

llvm-svn: 358686