Operating system specific args don't override args defined in the task

[tiagovcosta]

• VSCode Version: Code 1.19.1 (0759f77, 2017-12-19T09:35:14.671Z)
• OS Version: Darwin x64 17.3.0
• Extensions:

Extension	Author (truncated)	Version
vscode-eslint	dba	1.4.3
tslint	eg2	1.0.24
python	ms-	0.9.1
cpptools	ms-	0.14.5
debugger-for-chrome	msj	4.0.0
cmake	twx	0.0.17

---

Using the task below:

{
            "label": "build test",
            "type": "shell",
            "options": {
                "cwd": "${workspaceRoot}/build/debug"
            },
            "command": "make",
            "args": [
                "-j", "8"
            ],
            "osx": {
                "command": "xcodebuild build",
                "args": ["oops"],
            },
            "problemMatcher": {
                "owner": "cpp",
                "fileLocation": [
                    "absolute"
                ],
                "pattern": {
                    "regexp": "^(.*):(\\d+):(\\d+):\\s+(warning|error|fatal error):\\s+(.*)$",
                    "file": 1,
                    "line": 2,
                    "column": 3,
                    "severity": 4,
                    "message": 5
                }
            },
            "group": "build"
}

If I run it on MacOS, the command xcodebuild build -j 8 oops is executed instead of the expected xcodebuild build oops (as described in the docs)

Looks like platform specific args are being appended instead of overriding.

Reproduces without extensions: Yes

[chrmarti]

Verified. Note that the above task will be run as 'xcodebuild build' oops resulting a 'command not found: xcodebuild build' error.