Update BoringSSL to c239ffd0552179f358de31517391679e9b62ccd3 (#378)

* Various vendor script fixes:

- Fix various 'gsed' occurrences with '$sed'
- Remove the delocate patch, it is no longer required
- Add another patch to include inttypes in
  CNIOBoringSSL/crypto/x509/t_x509.c where PRIu64 is used and remove it
  from CNIOBoringSSL_bn.h. this works around a build failure with
  xcodeproj.
- Use the host platform build directory when mangling C++ symbols
- Fix Python bytes/string writing in build-asm.py

* Update BoringSSL to c239ffd0552179f358de31517391679e9b62ccd3

Package.swift

@@ -26,7 +26,7 @@ import class Foundation.ProcessInfo
 // Sources/CNIOBoringSSL directory. The source repository is at
 // https://boringssl.googlesource.com/boringssl.
 //
-// BoringSSL Commit: 1e469e45a46ff580899cbef939babe02ad916c85
+// BoringSSL Commit: c239ffd0552179f358de31517391679e9b62ccd3
 
 /// This function generates the dependencies we want to express.
 ///