update swift-system dependency to upToNextMinor instead of upToNextMajor (#270)
update swift-system dependency to upToNextMinor instead of upToNextMajor (#270)

motivation: align with SwiftPM and reduce risk

changes: 
* update swift-system dependency to upToNextMinor instead of upToNextMajor
* update min version of swift-system to 1.1.1
apple/swift-tools-support-core,apple/swift-tools-support-core,apple/swift-tools-support-core,apple/swift-tools-support-core