task.json

{
    "version": "2.0.0",
    "tasks": [
        {
            "label": "mkdir",
            "type": "shell",
            "command": "mkdir",
            "args": [
                "-p",
                "build"
            ],
        },
        {
            "label": "cmake",     // 命令的别名
            "type": "shell",         
            "command": "cmake",    // 命令
            "args": [                         // 参数列表
                ".."
            ],
            "options": {
                "cwd": "${workspaceFolder}/build", // 该命令的工作目录
            },
            "dependsOn": [   // 该命令执行前应该执行的命令
                "mkdir" 
            ]
        },
        {
            "label": "make",
            "type": "shell",
            "command": "make",
            "args": [],
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "options": {
                "cwd": "${workspaceFolder}/build",
            },
            "dependsOn": [
                "cmake"
            ]
        }
    ]
}

launch.json

{
    "version": "0.2.0",
    "configurations": [
        {
            "name": "(gdb) Launch",
            "type": "cppdbg",
            "request": "launch",
            "program": "${workspaceFolder}/build/bin/main", //cmake编译后输出的可执行文件的位置
            "args": [],
            "stopAtEntry": false,
            "cwd": "${workspaceFolder}/build",
            "environment": [],
            "externalConsole": false,
            "MIMode": "gdb",
            "miDebuggerPath": "/usr/bin/gdb",
            "setupCommands": [
                {
                    "description": "Enable pretty-printing for gdb",
                    "text": "-enable-pretty-printing",
                    "ignoreFailures": true
                }
            ],
            "preLaunchTask": "make"
        }
    ]
}

参考：https://www.jianshu.com/p/c3806d2ad1f8