[lldb] Update two API tests to fix x86 Darwin failures (llvm#121380)

The Intel Darwin CI bots had their Xcode updated, which brought in a
debugserver with Brendan Shanks' change from September
7281e0c
llvm#108663 where four general
purpose registers are sent by debugserver when in certain process
states. But most processes (nearly all in the testsuite) do not have
these registers available, so we will get register read failures when
requesting those four. These two tests would flag those as errors. There
would have been an additional problem with the g/G packet (which lldb
doesn't use w/ debugserver, but the testsuite tests) if placeholder
values were not included in the full register context bytes; I fixed
that issue with the SME patch to debugserver recently already.

lldb/packages/Python/lldbsuite/test/tools/lldb-server/gdbremote_testcase.py

@@ -1410,7 +1410,17 @@ def read_register_values(self, reg_infos, endian, thread_id=None):
             p_response = context.get("p_response")
             self.assertIsNotNone(p_response)
             self.assertTrue(len(p_response) > 0)
-            self.assertFalse(p_response[0] == "E")
+
+            # on x86 Darwin, 4 GPR registers are often
+            # unavailable, this is expected and correct.
+            if (
+                self.getArchitecture() == "x86_64"
+                and self.platformIsDarwin()
+                and p_response[0] == "E"
+            ):
+                values[reg_index] = 0
+            else:
+                self.assertFalse(p_response[0] == "E")
 
             values[reg_index] = unpack_register_hex_unsigned(endian, p_response)
 

lldb/test/API/commands/register/register/register_command/TestRegisters.py

@@ -58,6 +58,13 @@ def test_register_commands(self):
             # could not be read.  This is expected.
             error_str_matched = True
 
+        if self.getArchitecture() == "x86_64" and self.platformIsDarwin():
+            # debugserver on x86 will provide ds/es/ss/gsbase when the
+            # kernel provides them, but most of the time they will be
+            # unavailable.  So "register read -a" will report that
+            # 4 registers were unavailable, it is expected.
+            error_str_matched = True
+
         self.expect(
             "register read -a",
             MISSING_EXPECTED_REGISTERS,