Drop Xcode 10 support

Makefile

@@ -5,11 +5,6 @@ TEMPORARY_FOLDER=./tmp_portable_licenseplist
 build:
 	swift build --disable-sandbox -c release
 
-# For CocoaPods distribution
-# Works only on Xcode 10.1(Swift 4.2) or earlier
-build_legacy:
-	swift build --disable-sandbox -c release -Xswiftc -static-stdlib
-
 test:
 	swift test
 
@@ -26,7 +21,7 @@ install: build
 	mkdir -p "$(PREFIX)/bin"
 	cp -f ".build/release/license-plist" "$(PREFIX)/bin/license-plist"
 
-portable_zip: build_legacy
+portable_zip: build
 	mkdir -p "$(TEMPORARY_FOLDER)"
 	cp -f ".build/release/license-plist" "$(TEMPORARY_FOLDER)/license-plist"
 	cp -f "LICENSE" "$(TEMPORARY_FOLDER)"

release.sh

@@ -67,7 +67,7 @@ github-release upload \
 rm $lib_name.zip
 
 # CocoaPods
-DEVELOPER_DIR=/Applications/Xcode-10.1.app/Contents/Developer make portable_zip
+make portable_zip
 portable_zip_name="portable_licenseplist.zip"
 github-release upload \
     --user mono0926 \