Add modulemap for gRPC core

gRPC-Core.podspec

@@ -56,6 +56,8 @@ Pod::Spec.new do |s|
   s.module_name = name
   s.header_dir = name
 
+  s.module_map = 'include/grpc/module.modulemap'
+
   s.source_files = 'src/core/lib/profiling/timers.h',
                    'src/core/lib/support/backoff.h',
                    'src/core/lib/support/block_annotate.h',

include/grpc/module.modulemap

@@ -0,0 +1,5 @@
+framework module grpc {
+  umbrella header "grpc.h"
+  export *
+  module * { export * }
+}

templates/gRPC-Core.podspec.template

@@ -74,6 +74,8 @@
     s.module_name = name
     s.header_dir = name
 
+    s.module_map = 'include/grpc/module.modulemap'
+
     s.source_files = ${(',\n' + 19*' ').join('\'%s\'' % f for f in grpc_files(libs))}
 
     s.private_header_files = ${(',\n' + 27*' ').join('\'%s\'' % f for f in grpc_private_headers(libs))}