[lldb] Generic base for testing gdb-remote behavior

Summary:
Adds new utilities that make it easier to write test cases for lldb acting as a client over a gdb-remote connection.

- A GDBRemoteTestBase class that starts a mock GDB server and provides an easy way to check client packets
- A MockGDBServer that, via MockGDBServerResponder, can be made to issue server responses that test client behavior.
- Utility functions for handling common data encoding/decoding
- Utility functions for creating dummy targets from YAML files

----

Split from the review at https://reviews.llvm.org/D42145, which was a new feature that necessitated the new testing capabilities.

Reviewers: clayborg, labath

Reviewed By: clayborg, labath

Subscribers: hintonda, davide, jingham, krytarowski, mgorny, lldb-commits

Differential Revision: https://reviews.llvm.org/D42195
Patch by Owen Shaw <llvm@owenpshaw.net>

llvm-svn: 323636

lldb/packages/Python/lldbsuite/test/functionalities/gdb_remote_client/TestGDBRemoteClient.py

@@ -0,0 +1,13 @@
+import lldb
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.decorators import *
+from gdbclientutils import *
+
+
+class TestGDBRemoteClient(GDBRemoteTestBase):
+
+    def test_connect(self):
+        """Test connecting to a remote gdb server"""
+        target = self.createTarget("a.yaml")
+        process = self.connect(target)
+        self.assertPacketLogContains(["qProcessInfo", "qfThreadInfo"])

lldb/packages/Python/lldbsuite/test/functionalities/gdb_remote_client/a.yaml

@@ -0,0 +1,34 @@
+!ELF
+FileHeader:
+  Class:           ELFCLASS32
+  Data:            ELFDATA2LSB
+  Type:            ET_EXEC
+  Machine:         EM_ARM
+Sections:
+  - Name:            .text
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC, SHF_EXECINSTR ]
+    Address:         0x1000
+    AddressAlign:    0x4
+    Content:         "c3c3c3c3"
+  - Name:            .data
+    Type:            SHT_PROGBITS
+    Flags:           [ SHF_ALLOC ]
+    Address:         0x2000
+    AddressAlign:    0x4
+    Content:         "3232"
+ProgramHeaders:
+  - Type: PT_LOAD
+    Flags: [ PF_X, PF_R ]
+    VAddr: 0x1000
+    PAddr: 0x1000
+    Align: 0x4
+    Sections:
+      - Section: .text
+  - Type: PT_LOAD
+    Flags: [ PF_R, PF_W ]
+    VAddr: 0x2000
+    PAddr: 0x1004
+    Align: 0x4
+    Sections:
+      - Section: .data