Issue Description:

james@james-Inspiron-580:~$ uname -a
Linux james-Inspiron-580 4.18.0-15-generic #16~18.04.1-Ubuntu SMP Thu Feb 7 14:06:04 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

james@james-Inspiron-580:~$ swift --version
Swift version 4.2.2 (swift-4.2.2-RELEASE)
Target: x86_64-unknown-linux-gnu

//

import Foundation

let date = Date()

james@james-Inspiron-580:~$ swift xdate.sw
<unknown>:0: error: fatal error encountered during compilation; please file a bug report with your project and the crash log
<unknown>:0: note: Program used external function '$S10Foundation4DateVACycfC' which could not be resolved!
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0x3defe74]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0x3dedc8c]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0x3df0032]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x12890)[0x7f1746a01890]
/lib/x86_64-linux-gnu/libc.so.6(gsignal+0xc7)[0x7f1744e64e97]
/lib/x86_64-linux-gnu/libc.so.6(abort+0x141)[0x7f1744e66801]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0x4b4f46]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0x3d9049c]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0xffba8f]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0xffa655]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0xfe832d]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0x4cd1e8]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0x4b408a]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0x4afdc0]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0x46ae38]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xe7)[0x7f1744e47b97]
/swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift[0x46904a]
Stack dump:
0. Program arguments: /swift/swift-4.2.2-RELEASE-ubuntu18.04/usr/bin/swift -frontend -interpret xdate.sw -disable-objc-interop -color-diagnostics -module-name xdate
Aborted (core dumped)
james@james-Inspiron-580:~$ uname -r

Discovered Foundation uses libcurl. After installation of libcurl3, the problem got worse. Then replaced with libcurl4, problem was fixed. Note that while the Date class functions, the compiler shouldn't abort.

Leaving the bug for now.