Update macOS minimum deployment target from 10.15.0 to 10.15.4 to allow Swift-friendlier Foundation.FileHandle APIs to be used in SwiftPM. As SourceKit-LSP uses libSwiftPM, it needs to have as new of a deployment target as SwiftPM does. This has no change in behavior in SourceKit-LSP. (#436)

Author: abertelrud

Package.swift

@@ -4,7 +4,7 @@ import PackageDescription
 
 let package = Package(
     name: "SourceKitLSP",
-    platforms: [.macOS(.v10_15)],
+    platforms: [.macOS("10.15.4")],
     products: [
       .executable(
         name: "sourcekit-lsp",