Pass sdk option to Swift compiler for WASI triples

[MaxDesiatov]

When building for WebAssembly/WASI swiftc needs the -sdk option passed to it with the sdk path.

[neonichu]

@swift-ci please smoke test

[MaxDesiatov]

The Linux failures are:

/home/buildnode/jenkins/workspace/swift-package-manager-Linux-smoke-test/branch-master/swiftpm/Tests/PackageLoadingTests/PD4LoadingTests.swift:409: error: PackageDescription4LoadingTests.testEmptyProductTargets : failed - No diagnostics left to check
12:50:53 Test Case 'PackageDescription4LoadingTests.testEmptyProductTargets' failed (0.793 seconds)
12:50:53 Test Suite 'PackageDescription4LoadingTests' failed at 2020-05-07 12:50:36.011
12:50:53 	 Executed 1 test, with 1 failure (0 unexpected) in 0.793 (0.793) seconds
12:50:53 Test Suite 'Selected tests' failed at 2020-05-07 12:50:36.011
12:50:53 	 Executed 1 test, with 1 failure (0 unexpected) in 0.793 (0.793) seconds
12:50:53 
12:50:53 Test Suite 'Selected tests' started at 2020-05-07 12:50:35.193
12:50:53 Test Suite 'PackageDescription4LoadingTests' started at 2020-05-07 12:50:35.195
12:50:53 Test Case 'PackageDescription4LoadingTests.testCTarget' started at 2020-05-07 12:50:35.195
12:50:53 <unknown>:0: warning: missing submodule 'CoreFoundation'
12:50:53 <unknown>:0: error: missing required module 'CoreFoundation'
12:50:53 /home/buildnode/jenkins/workspace/swift-package-manager-Linux-smoke-test/branch-master/swiftpm/Tests/PackageLoadingTests/PDLoadingTests.swift:235: error: PackageDescription4LoadingTests.testCTarget : failed - 

Do you think that's related?

[neonichu]

Doesn't seem likely to be related, let's try re-running the tests.

[neonichu]

@swift-ci please smoke test