panic: Unknown OS: linux-arm [recovered]
        panic: Unknown OS: linux-arm

goroutine 12 [running]:
testing.func·006()
        /usr/local/go/src/testing/testing.go:441 +0x188
arduino.cc/builder/test.translateGOOSGOARCHToPackageIndexValue(0x0, 0x0, 0x0)
        /root/arduino-builder/src/arduino.cc/builder/test/helper_tools_downloader.go:704 +0x20c
arduino.cc/builder/test.downloadTools(0x107fdd74, 0x5, 0x5, 0x10736d60, 0x0, 0x0)
        /root/arduino-builder/src/arduino.cc/builder/test/helper_tools_downloader.go:283 +0x30
arduino.cc/builder/test.download(0x107ca600, 0x107fdca4, 0x2, 0x2, 0x107fdc60, 0x1, 0x1, 0x107fdc40, 0x1, 0x1, ...)
        /root/arduino-builder/src/arduino.cc/builder/test/helper_tools_downloader.go:187 +0x39c
arduino.cc/builder/test.DownloadCoresAndToolsAndLibraries(0x107ca600)
        /root/arduino-builder/src/arduino.cc/builder/test/helper_tools_downloader.go:141 +0x334
arduino.cc/builder/test.TestBuilderEmptySketch(0x107ca600)
        /root/arduino-builder/src/arduino.cc/builder/test/builder_test.go:43 +0x2c
testing.tRunner(0x107ca600, 0x590f80)
        /usr/local/go/src/testing/testing.go:447 +0xf4
created by testing.RunTests
        /usr/local/go/src/testing/testing.go:555 +0x7e0

goroutine 1 [chan receive]:
testing.RunTests(0x494e74, 0x590f38, 0xd0, 0xd0, 0xb6e10d01)
        /usr/local/go/src/testing/testing.go:556 +0x814
testing.(*M).Run(0x107301e0, 0x5962d8)
        /usr/local/go/src/testing/testing.go:485 +0x74
main.main()
        arduino.cc/builder/test/_test/_testmain.go:466 +0x1b4

goroutine 15 [IO wait]:
net.(*pollDesc).Wait(0x10728ab8, 0x72, 0x0, 0x0)
        /usr/local/go/src/net/fd_poll_runtime.go:84 +0x3c
net.(*pollDesc).WaitRead(0x10728ab8, 0x0, 0x0)
        /usr/local/go/src/net/fd_poll_runtime.go:89 +0x38
net.(*netFD).Read(0x10728a80, 0x10735000, 0x1000, 0x1000, 0x0, 0xb6e10b68, 0x10790018)
        /usr/local/go/src/net/fd_unix.go:242 +0x390
net.(*conn).Read(0x1071a3d8, 0x10735000, 0x1000, 0x1000, 0x0, 0x0, 0x0)
        /usr/local/go/src/net/net.go:121 +0xc8
net/http.noteEOFReader.Read(0xb6e121c8, 0x1071a3d8, 0x107ca14c, 0x10735000, 0x1000, 0x1000, 0x391d30, 0x0, 0x0)
        /usr/local/go/src/net/http/transport.go:1270 +0x78
net/http.(*noteEOFReader).Read(0x10790bc0, 0x10735000, 0x1000, 0x1000, 0x10710000, 0x0, 0x0)
        <autogenerated>:125 +0xec
bufio.(*Reader).fill(0x107304b0)
        /usr/local/go/src/bufio/bufio.go:97 +0x1d8
bufio.(*Reader).Peek(0x107304b0, 0x1, 0x0, 0x0, 0x0, 0x0, 0x0)
        /usr/local/go/src/bufio/bufio.go:132 +0xd4
net/http.(*persistConn).readLoop(0x107ca120)
        /usr/local/go/src/net/http/transport.go:842 +0x88
created by net/http.(*Transport).dialConn
        /usr/local/go/src/net/http/transport.go:645 +0xba0

goroutine 17 [syscall, locked to thread]:
runtime.goexit()
        /usr/local/go/src/runtime/asm_arm.s:1322 +0x4

goroutine 16 [select]:
net/http.(*persistConn).writeLoop(0x107ca120)
        /usr/local/go/src/net/http/transport.go:945 +0x320
created by net/http.(*Transport).dialConn
        /usr/local/go/src/net/http/transport.go:645 +0xbc8