Alias of systemLibrary module can be omitted

Using Swift
1

Hi community,

I've tried to import modules from external packages.

The two modules have same name bar.
The MyLib/bar is a swift module.
The MyLib2/bar is a systemLibrary module in C language.

So, I tried the module aliases. But it seems that the module aliasing
works differently on systemLibrary than normal swift module. For normal
swift modules with same names, I need to give different aliases to all
the modules. For systemLibrary, its alias name can not be used for import
and its alias can be omitted.

$ tree --charset C
.
|-- MyApp
|   |-- Package.swift
|   `-- Sources
|       `-- MyApp
|           `-- MyApp.swift
|-- MyLib
|   |-- Package.swift
|   `-- Sources
|       `-- bar
|           `-- bar.swift
`-- MyLib2
    |-- Package.swift
    `-- Sources
        |-- Makefile
        |-- MyLib
        |   `-- MyLib.swift
        |-- bar
        |   |-- Makefile
        |   |-- bar.c
        |   |-- bar.h
        |   `-- module.modulemap
        `-- build
            `-- bar
                |-- bar
                |-- bar.d
                |-- bar.o
                |-- libbar.1.2.3.dylib
                |-- libbar.1.dylib -> libbar.1.2.3.dylib
                `-- libbar.dylib -> libbar.1.2.3.dylib

$ 

.executableTarget(
    name: "MyApp",
    dependencies: [
        .product(name: "bar", package: "MyLib", moduleAliases: ["bar": "bar1"]),
        .product(name: "bar", package: "MyLib2"),
    ]
),

// MyLib
.library( name: "bar", targets: ["bar"]),
.target( name: "bar", dependencies: []),

// MyLib2
.library( name: "bar", targets: ["bar"]),
.systemLibrary( name: "bar"),