clang: error: no such file or directory on Ubuntu 18.04.1 fails to build

[IgorMuzyka]

Hi. I'm totally not sure what am i doing wrong. And i have noticed that your library has Ubuntu 16.04 badge and not 18.04. But anyway i'm hoping to get some help. Here is the error swift trows at me.

Linking ./.build/x86_64-unknown-linux/debug/backendPackageTests.xctest
clang: error: no such file or directory: '/home/igor/.../.build/x86_64-unknown-linux/debug/VaporTestTools.build/Extensions/Response'
clang: error: no such file or directory: 'tools/Response+Checks.swift.o'
clang: error: no such file or directory: '/home/igor/.../.build/x86_64-unknown-linux/debug/VaporTestTools.build/Extensions/Response'
clang: error: no such file or directory: 'tools/Response+Debug.swift.o'
clang: error: no such file or directory: '/home/igor/.../.build/x86_64-unknown-linux/debug/VaporTestTools.build/Extensions/Response'
clang: error: no such file or directory: 'tools/Response+Decoding.swift.o'
clang: error: no such file or directory: '/home/igor/.../.build/x86_64-unknown-linux/debug/VaporTestTools.build/Extensions/Response'
clang: error: no such file or directory: 'tools/Response+Getters.swift.o'
<unknown>:0: error: link command failed with exit code 1 (use -v to see invocation)
error: terminated(1): /home/igor/.swiftenv/versions/4.2/usr/bin/swift-build-tool -f /home/igor/.../.build/debug.yaml test output:

As you may see it says no such file or directory tool/Response+Getters.swift.o which seems pretty weird to me.
Any suggestions?