The “Swift Language Version” (SWIFT_VERSION) build setting must be set to a supported value for targets which use Swift

[billzt]

I make a Cartfile in my base directory and write:

github "maximveksler/GeohashKit"

Then I run: carthage update --use-submodules

It failed! It says:

usr/bin/xcrun xcodebuild -project /Users/zhutao/Documents/xcode/geohash/geohash/Carthage/Checkouts/GeohashKit/GeohashKit.xcodeproj -scheme GeohashKit -configuration Release -derivedDataPath /Users/zhutao/Library/Caches/org.carthage.CarthageKit/DerivedData/9.1_9B55/GeohashKit/0.1 ONLY_ACTIVE_ARCH=NO CODE_SIGNING_REQUIRED=NO CODE_SIGN_IDENTITY= CARTHAGE=YES archive -archivePath ./ SKIP_INSTALL=YES GCC_INSTRUMENT_PROGRAM_FLOW_ARCS=NO CLANG_ENABLE_CODE_COVERAGE=NO (launched in /Users/zhutao/Documents/xcode/geohash/geohash/Carthage/Checkouts/GeohashKit)User defaults from command line:
    IDEArchivePathOverride = /Users/zhutao/Documents/xcode/geohash/geohash/Carthage/Checkouts/GeohashKit
    IDEDerivedDataPathOverride = /Users/zhutao/Library/Caches/org.carthage.CarthageKit/DerivedData/9.1_9B55/GeohashKit/0.1

Build settings from command line:
    CARTHAGE = YES
    CLANG_ENABLE_CODE_COVERAGE = NO
    CODE_SIGN_IDENTITY =
    CODE_SIGNING_REQUIRED = NO
    GCC_INSTRUMENT_PROGRAM_FLOW_ARCS = NO
    ONLY_ACTIVE_ARCH = NO
    SKIP_INSTALL = YES

=== BUILD TARGET GeohashKit OF PROJECT GeohashKit WITH CONFIGURATION Release ===

Check dependencies
The “Swift Language Version” (SWIFT_VERSION) build setting must be set to a supported value for targets which use Swift. This setting can be set in the build settings editor.

** ARCHIVE FAILED **


The following build commands failed:
        Check dependencies
(1 failure)

My carthage version is 0.26.2 and my Xcode version is 9.1