Make _NumericsShims a systemLibrary target.

Author: stephentyrone

Package.swift

@@ -50,10 +50,8 @@ let package = Package(
     ),
 
     // MARK: - Implementation details
-    .target(
-      name: "_NumericsShims",
-      dependencies: [],
-      exclude: excludedFilenames
+    .systemLibrary(
+      name: "_NumericsShims"
     ),
 
     .target(

Sources/_NumericsShims/_NumericsShims.c

@@ -1,3 +1,4 @@
 module _NumericsShims {
   header "_NumericsShims.h"
+  link "m"
 }