Undef. symbols when linking SwiftPM

Compiling Swift Module 'swift_build' (3 sources)
Link /home/wdillon/build/Ninja-ReleaseAssert/swiftpm-linux-armv7/.bootstrap/bin/swift-build
bootstrap: note: building self-hosted 'swift-build': env SWIFTC=/home/wdillon/build/Ninja-ReleaseAssert/swift-linux-armv7/bin/swiftc SWIFT_BUILD_TOOL=/home/wdillon/build/Ninja-ReleaseAssert/llbuild-linux-armv7/bin/swift-build-tool SWIFT_BUILD_PATH=/home/wdillon/build/Ninja-ReleaseAssert/swiftpm-linux-armv7 SWIFTPM_EMBED_RPATH=$ORIGIN/../lib/swift/linux /home/wdillon/build/Ninja-ReleaseAssert/swiftpm-linux-armv7/.bootstrap/bin/swift-build
LLVM ERROR: Program used external function '_TMaC18PackageDescription7Package' which could not be resolved!
error: ExitStatus(1, ["/home/wdillon/build/Ninja-ReleaseAssert/swift-linux-armv7/bin/swiftc", "--driver-mode=swift", "-I", "/home/wdillon/build/Ninja-ReleaseAssert/swiftpm-linux-armv7/.bootstrap/lib/swift/pm", "-L", "/home/wdillon/build/Ninja-ReleaseAssert/swiftpm-linux-armv7/.bootstrap/lib/swift/pm", "-lPackageDescription", "/home/wdillon/swiftpm/Package.swift"])
bootstrap: error: build failed with exit status 1
utils/build-script: command terminated with a non-zero exit status 1, aborting