Linking failure in open-source Swift project - swift

Question

I've been following the "Getting Started" tutorial on http://swift.org. Upon creating new Swift "Hello World" project, I ran shell command:
$ swift build
and got the following output:
Compiling Swift Module 'MyProject' (1 sources)
Linking MyProject
ld: library not found for -lobjc
<unknown>:0: error: build had 1 command failures
error: exit(1): /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2016-02-25-a.xctoolchain/usr/bin/swift-build-tool -f /Users/petrmanek/Projekty/MyProject/.build/debug.yaml default
I'm assuming that ld: library not found for -lobjc means that the linker can't find the Objective-C standard library, however I find that hard to believe as both files /usr/lib/libobjc.A.dylib and /usr/lib/libobjc.dylib are present on my file system.
What do I do now?
My configuration is:
Hardware: Mac mini (Late 2012)
OS: Mac OS 10.11 El Capitan
uname -a
Darwin tywin 15.3.0 Darwin Kernel Version 15.3.0: Thu Dec 10 18:40:58 PST 2015; root:xnu-3248.30.4~1/RELEASE_X86_64 x86_64
swift --version
Apple Swift version 3.0-dev (LLVM b361b0fc05, Clang 11493b0f62, Swift fc261045a5)
Target: x86_64-apple-macosx10.9

Answer 1

I think I have solved it. Here's my solution if anyone's interested.
Looking at the swift-build --help option list, I have discovered the option -Xlinker which allows me to specify flags directly for ld. I used this option to tell it to be more verbose with command:
$ swift build -Xlinker -v
The output was:
Linking MyProject
#(#)PROGRAM:ld PROJECT:ld64-242
configured to support archs: i386 x86_64 x86_64h armv6 armv7 armv7s armv7m armv7k arm64
Library search paths:
/Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2016-02-25-a.xctoolchain/usr/lib/swift/macosx
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/lib
Framework search paths:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/System/Library/Frameworks/
ld: library not found for -lobjc
<unknown>:0: error: build had 1 command failures
error: exit(1): /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2016-02-25-a.xctoolchain/usr/bin/swift-build-tool -f /Users/petrmanek/Projekty/MyProject/.build/debug.yaml default
This was quite messy but we can see that /usr/lib is not among the library search paths. I had two options:
add /usr/lib as a search path - that didn't work because ld strives to add /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/ prefix in front of every search path I add using the -L flag
link `libobjc.dylib - that worked
Here are the shell commands I used (I did the same thing for libSystem because it required the same treatment):
$ cd /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2016-02-25-a.xctoolchain/usr/lib/swift/macosx
$ sudo ln -s /usr/lib/libobjc.dylib
$ sudo ln -s /usr/lib/libSystem.dylib
The swift build command is working now and the product runs correctly. However, I don't believe that is user-friendly installation process, Apple.