Add a check for a linker bug which will cause the test to fail.

Author: jimingham

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

@@ -27,6 +27,18 @@ def do_test(self):
         # Make sure that we did manage to generate a branch island for foo:
         syms = target.FindSymbols("foo.island", lldb.eSymbolTypeCode)
         self.assertEqual(len(syms), 1, "We did generate an island for foo")
+        # There's a bug in the Xcode 15.2 linker, where it did not emit
+        # "function starts" entries for the branch island symbols, which
+        # causes lldb to set the range of the previous non-island symbol to
+        # encompass the range of the branch island symbols.  If we encounter
+        # that bug, then we won't successfully do the step in.  Test for
+        # that here - if the symbol doesn't round-trip from
+        # name->address->name then the rest of the test can't pass.
+        island_sym_ctx = syms[0]
+        sym_addr = island_sym_ctx.symbol.addr
+        resolved_name = sym_addr.symbol.name
+        if resolved_name != "foo.island":
+            return
 
         thread.StepInto()
         stop_frame = thread.frames[0]