使用 Swift DEVELOPMENT-SNAPSHOT-2016-02-08-a，我正在尝试使用构建一个项目，swift build但是一旦添加该行import Foundation，我就会收到错误消息：
[I] ~/Dropbox/Projects/test
↪ swift build --clean; and swift build
Compiling Swift Module 'test' (1 sources)
<unknown>:0: error: cannot load underlying module for 'CoreGraphics'
<unknown>:0: note: did you forget to set an SDK using -sdk or SDKROOT?
<unknown>:0: note: use "xcrun -sdk macosx swiftc" to select the default OS X SDK installed with Xcode
<unknown>:0: error: build had 1 command failures
error: exit(1): ["/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2016-02-08-a.xctoolchain/usr/bin/swift-build-tool", "-f", "/Users/me/Dropbox/Projects/test/.build/debug/test.o/llbuild.yaml"]
运行xcrun -sdk macosx导致“没有这样的 SDK：'machos'”错误：
↪ xcrun -sdk macosx swift build 0@10:34:03
<unknown>:0: warning: no such SDK: 'macosx'
<unknown>:0: warning: no such sysroot directory: 'macosx'
<unknown>:0: error: cannot load underlying module for 'Darwin'
error: exit(1): ["/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2016-02-08-a.xctoolchain/usr/bin/swiftc", "--driver-mode=swift", "-I", "/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2016-02-08-a.xctoolchain/usr/lib/swift/pm", "-L", "/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2016-02-08-a.xctoolchain/usr/lib/swift/pm", "-lPackageDescription", "-target", "x86_64-apple-macosx10.10", "/Users/me/Dropbox/Projects/test/Package.swift"]
这仅适用于 main.swift，其内容为：
import Foundation
print("Hello, world!")
Packages.swift 中没有定义依赖项。
真的不知道这里发生了什么。这在我的 Ubuntu 14.04 DigitalOcean VPS 以及 Xcode 7.3 Beta 5 中编译得很好。
OS X 10.11.3
↪ swift --version 0@10:21:16
Apple Swift version 3.0-dev (LLVM a7663bb722, Clang 4ca3c7fa28, Swift 1c2f40e246)
Target: x86_64-apple-macosx10.9