Make BoringSSL work with frameworks

Cocoapods 1.0 keeps the directory structure of the public headers when
creating a dynamic framework, so if we keep the header_mappings_dir as it
was, includes would need to be of the form #include <openssl/openssl/ssl.h>

This means our header_mappings_dir has to be ‘include/openssl’ instead of
‘include’. Which in turn means that, for static libraries, we have to tell
Cocoapods to prepend an ‘openssl’ directory to the headers. We do that
with the ‘header_dir’ attribute of the podspec.

src/objective-c/BoringSSL.podspec

@@ -31,7 +31,7 @@
 
 Pod::Spec.new do |s|
   s.name     = 'BoringSSL'
-  s.version  = '2.0'
+  s.version  = '3.0'
   s.summary  = 'BoringSSL is a fork of OpenSSL that is designed to meet Google’s needs.'
   # Adapted from the homepage:
   s.description = <<-DESC
@@ -69,15 +69,19 @@ Pod::Spec.new do |s|
   s.source = { :git => 'https://boringssl.googlesource.com/boringssl',
                :tag => 'version_for_cocoapods_2.0' }
 
+  name = 'openssl'
+  s.module_name = name
+  s.header_dir = name
+
   s.source_files = 'ssl/*.{h,c}',
                    'ssl/**/*.{h,c}',
                    '*.{h,c}',
                    'crypto/*.{h,c}',
                    'crypto/**/*.{h,c}',
                    'include/openssl/*.h'
-
   s.public_header_files = 'include/openssl/*.h'
-  s.header_mappings_dir = 'include'
+  s.header_mappings_dir = 'include/openssl'
+  s.module_map = 'include/openssl/module.modulemap'
 
   s.exclude_files = "**/*_test.*"
 
@@ -92,6 +96,25 @@ Pod::Spec.new do |s|
     # included it in every bridged header).
     sed -E -i '.back' 's/\\*I,/*i,/g' include/openssl/rsa.h
 
+    # Replace `#include "../crypto/internal.h"` in e_tls.c with `#include "../internal.h"`. The
+    # former assumes crypto/ is in the headers search path, which is hard to enforce when using
+    # dynamic frameworks. The latters always works, being relative to the current file.
+    sed -E -i '.back' 's/crypto\\///g' crypto/cipher/e_tls.c
+
+    # Add a module map and an umbrella header
+    cat > include/openssl/umbrella.h <<EOF
+      #include "ssl.h"
+      #include "crypto.h"
+
+    EOF
+    cat > include/openssl/module.modulemap <<EOF
+      framework module openssl {
+        umbrella header "umbrella.h"
+        export *
+        module * { export * }
+      }
+    EOF
+
     # This is a bit ridiculous, but requiring people to install Go in order to build is slightly
     # more ridiculous IMO. To save you from scrolling, this is the last part of the podspec.
     # TODO(jcanizales): Translate err_data_generate.go into a Bash or Ruby script.