swiftソースがあるディレクトリに下記Makefileを置く。
Makefile
SWIFT=/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift
SDKPATH=/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator8.0.sdk
SDK=-sdk $(SDKPATH)
OPTIONS=-parse -DDEBUG=1 -target i386-apple-ios8.0
check-syntax:
$(SWIFT) $(SDK) $(OPTIONS) ${CHK_SOURCES}