Remove extra paths added to LD_LIBRARY_PATH on Linux when running tests

These break running tests when there's already a swift on PATH that
isn't the swift currently being run. There shouldn't be a need for these
as the run path of the compiled binary is already the correct path (ie.
the library path of the swift that built it and `$ORIGIN`).

(cherry picked from commit 5c7db58)
(cherry picked from commit 07952dc)

Author: bnbarham

Sources/Commands/Utilities/TestingSupport.swift

@@ -141,16 +141,6 @@ enum TestingSupport {
         if let location = toolchain.xctestPath {
             env.prependPath("Path", value: location.pathString)
         }
-        #elseif os(Linux)
-        var libraryPaths = ["/usr/lib/swift/linux"]
-        if let path = env["PATH"], let firstPathEntry = path.components(separatedBy: ":").first {
-            libraryPaths.append("\(firstPathEntry)/../lib/swift/linux")
-        }
-        if let originalLibraryPaths = env["LD_LIBRARY_PATH"] {
-            libraryPaths.append(originalLibraryPaths)
-        }
-        // Pass this explicitly on Linux because XCTest started requiring it, rdar://103054033
-        env["LD_LIBRARY_PATH"] = libraryPaths.joined(separator: ":")
         #endif
         return env
         #else