build/dev: add vscode devcontainer and dhtnode task

.devcontainer/devcontainer.json

+{
+	"name": "C++",
+	"build": {
+		"dockerfile": "../docker/DockerfileDepsLlvm",
+	},
+	"runArgs": [ "--cap-add=SYS_PTRACE", "--security-opt", "seccomp=unconfined"],
+	"settings": {},
+	"extensions": [
+		"ms-vscode.cpptools"
+	],
+	"forwardPorts": [4222],
+}

.vscode/launch.json

+{
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "name": "dhtnode",
+            "type": "cppdbg",
+            "request": "launch",
+            "program": "${workspaceFolder}/build/tools/dhtnode",
+            "args": ["-v", "-p", "4222"],
+            "cwd": "${workspaceFolder}/build",
+            "environment": [],
+            "MIMode": "gdb",
+            "setupCommands": [
+                {
+                    "description": "Enable pretty-printing for gdb",
+                    "text": "-enable-pretty-printing",
+                    "ignoreFailures": true
+                }
+            ],
+            "preLaunchTask": "build"
+        }
+    ]
+}

.vscode/tasks.json

+{
+    "version": "2.0.0",
+    "tasks": [
+        {
+            "label": "build",
+            "type": "shell",
+            "options": {
+                "cwd": "${workspaceRoot}/build"
+            },
+            "command": "make",
+            "args": ["-j4"],
+            "dependsOn": "cmake"
+        },
+        {
+            "label": "cmake",
+            "type": "shell",
+            "options": {
+                "cwd": "${workspaceRoot}/build"
+            },
+            "command": "cmake",
+            "args": [
+                "${workspaceRoot}",
+                "-DCMAKE_BUILD_TYPE=Debug",
+                "-DOPENDHT_PROXY_CLIENT=On",
+                "-DOPENDHT_PROXY_SERVER=On",
+                "-DOPENDHT_C=On"
+            ],
+            "dependsOn": "builddir"
+        },
+        {
+            "label": "builddir",
+            "type": "shell",
+            "options": {
+                "cwd": "${workspaceRoot}"
+            },
+            "command": "mkdir",
+            "args": [
+                "-p",
+                "${workspaceRoot}/build"
+            ]
+        },
+    ]
+}

docker/DockerfileDepsLlvm

@@ -8,7 +8,7 @@ RUN apt-get update && apt-get install -y \
     && echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selections
 
 RUN apt-get update \
-    && apt-get install -y llvm llvm-dev clang make cmake pkg-config git wget libncurses5-dev libreadline-dev \
+    && apt-get install -y llvm llvm-dev lldb clang gdb make cmake pkg-config git wget libncurses5-dev libreadline-dev \
        nettle-dev libgnutls28-dev libuv1-dev libmsgpack-dev libjsoncpp-dev cython3 python3-dev \
        python3-setuptools libcppunit-dev python3-pip \
        autotools-dev autoconf libssl-dev libargon2-dev \