Add Xcode 12 carthage workaround to travis build

.travis.yml

@@ -24,7 +24,7 @@ before_install:
       gem install cocoapods -v '1.7.5';
       pod repo update;
     fi
-  - carthage bootstrap --platform "$SCHEME" --verbose
+  - ./carthage.sh bootstrap --platform "$SCHEME" --verbose
 
 install:
   - gem install xcpretty

carthage.sh

@@ -0,0 +1,19 @@
+# carthage.sh
+# Usage example: ./carthage.sh build --platform iOS
+
+set -euo pipefail
+
+xcconfig=$(mktemp /tmp/static.xcconfig.XXXXXX)
+trap 'rm -f "$xcconfig"' INT TERM HUP EXIT
+
+# For Xcode 12 make sure EXCLUDED_ARCHS is set to arm architectures otherwise
+# the build will fail on lipo due to duplicate architectures.
+
+CURRENT_XCODE_VERSION=$(xcodebuild -version | grep "Build version" | cut -d' ' -f3)
+echo "EXCLUDED_ARCHS__EFFECTIVE_PLATFORM_SUFFIX_simulator__NATIVE_ARCH_64_BIT_x86_64__XCODE_1200__BUILD_$CURRENT_XCODE_VERSION = arm64 arm64e armv7 armv7s armv6 armv8" >> $xcconfig
+
+echo 'EXCLUDED_ARCHS__EFFECTIVE_PLATFORM_SUFFIX_simulator__NATIVE_ARCH_64_BIT_x86_64__XCODE_1200 = $(EXCLUDED_ARCHS__EFFECTIVE_PLATFORM_SUFFIX_simulator__NATIVE_ARCH_64_BIT_x86_64__XCODE_1200__BUILD_$(XCODE_PRODUCT_BUILD_VERSION))' >> $xcconfig
+echo 'EXCLUDED_ARCHS = $(inherited) $(EXCLUDED_ARCHS__EFFECTIVE_PLATFORM_SUFFIX_$(EFFECTIVE_PLATFORM_SUFFIX)__NATIVE_ARCH_64_BIT_$(NATIVE_ARCH_64_BIT)__XCODE_$(XCODE_VERSION_MAJOR))' >> $xcconfig
+
+export XCODE_XCCONFIG_FILE="$xcconfig"
+carthage "$@"