Branch island no dsym (llvm#139191)

When we get to the branch island, we don't see the symbol for
    it.
    
    The only other thing I can think of that would be a dsymutil bug?
Let's try this just with dwarf, and then I'll have to revert all this
    and see if I can reproduce this locally somehow.

Author: jimingham

lldb/test/API/macosx/branch-islands/TestBranchIslands.py

@@ -15,7 +15,7 @@ class TestBranchIslandStepping(TestBase):
     @skipUnlessAppleSilicon
     def test_step_in_branch_island(self):
         """Make sure we can step in across a branch island"""
-        self.build()
+        self.build(debug_info="dwarf")
         self.main_source_file = lldb.SBFileSpec("main.c")
         self.do_test()