Pass objects to linker flags as is in macro test projects

These are absolute paths, no "-l" is necessary here and is actually an
error with eg. `ld.bfd`.

Author: bnbarham

Sources/SKTestSupport/SwiftPMTestProject.swift

@@ -133,7 +133,7 @@ package class SwiftPMTestProject: MultiFileTestProject {
 
       let linkerFlags = objectFiles.map {
         """
-        "-l", "\($0)",
+        "\($0)",
         """
       }.joined(separator: "\n")