Mark a few API uses in Swift Compiler Sources as unsafe.

Author: zoecarver

SwiftCompilerSources/Sources/Basic/SourceLoc.swift

@@ -57,7 +57,7 @@ public struct CharSourceRange {
   }
 
   public init?(bridged: swift.CharSourceRange) {
-    guard let start = SourceLoc(bridged: bridged.getStart()) else {
+    guard let start = SourceLoc(bridged: bridged.__getStartUnsafe()) else {
       return nil
     }
     self.init(start: start, byteLength: bridged.getByteLength())

SwiftCompilerSources/Sources/Basic/Utils.swift

@@ -65,7 +65,7 @@ extension String {
   /// Underscored to avoid name collision with the std overlay.
   /// To be replaced with an overlay call once the CI uses SDKs built with Swift 5.8.
   public init(_cxxString s: std.string) {
-    self.init(cString: s.c_str())
+    self.init(cString: s.__c_strUnsafe())
     withExtendedLifetime(s) {}
   }
 }