cmake SWIFT_STDLIB_HAS_ENVIRON examples

swiftlang/swift stdlib/cmake/modules/StdlibOptions.cmake :205 

option(SWIFT_STDLIB_HAS_ENVIRON
       "Build stdlib assuming the platform supports environment variables."
       TRUE)

swiftlang/swift stdlib/cmake/modules/SwiftSource.cmake :367 

list(APPEND result "-D" "SWIFT_STDLIB_HAS_ENVIRON")