Add missing cmake dependencies.

Author: ChrisCummins

compiler_gym/service/BUILD

@@ -13,7 +13,7 @@ py_library(
         ":compilation_session",
         ":connection",
         # TODO(github.com/facebookresearch/CompilerGym/pull/633):
-        # add this after circular dependencies are resolved
+        # add this after circular dependencies are resolved:
         # ":client_service_compiler_env",
         ":connection_pool",
         "//compiler_gym/service/proto",

compiler_gym/service/CMakeLists.txt

@@ -14,8 +14,9 @@ cg_py_library(
     ::compilation_session
     ::connection
     # TODO(github.com/facebookresearch/CompilerGym/pull/633):
-    # add this after circular dependencies are resolved
-    #::client_service_compiler_env
+    # add this after circular dependencies are resolved:
+    # ::client_service_compiler_env
+    ::connection_pool
     compiler_gym::service::proto::proto
   PUBLIC
 )
@@ -73,3 +74,13 @@ cg_py_library(
     compiler_gym::views::views
   PUBLIC
 )
+
+cg_py_library(
+  NAME
+    connection_pool
+  SRCS
+    "connection_pool.py"
+  DEPS
+    ::connection
+  PUBLIC
+)