fix(pubsub): install admin mocks (#13537)

Author: dbolduc

cmake/GoogleCloudCppCommon.cmake

@@ -47,6 +47,11 @@ function (google_cloud_cpp_install_headers target destination)
         get_target_property(target_sources ${target} SOURCES)
     endif ()
     foreach (header ${target_sources})
+        # Sometimes we use generator expressions for the headers.
+        string(REPLACE "$<BUILD_INTERFACE:" "" header "${header}")
+        string(REPLACE ">" "" header "${header}")
+
+        # Only install headers.
         if (NOT "${header}" MATCHES "\\.h$" AND NOT "${header}" MATCHES
                                                 "\\.inc$")
             continue()

google/cloud/pubsub/CMakeLists.txt

@@ -519,14 +519,8 @@ install(
     TARGETS google_cloud_cpp_pubsub_mocks
     EXPORT pubsub_mocks-targets
     COMPONENT google_cloud_cpp_development)
-install(
-    FILES ${google_cloud_cpp_pubsub_mocks_hdrs}
-    DESTINATION "include/google/cloud/pubsub/mocks"
-    COMPONENT google_cloud_cpp_development)
-install(
-    FILES ${google_cloud_cpp_pubsub_mocks_hdrs}
-    DESTINATION "include/google/cloud/pubsub/admin/mocks"
-    COMPONENT google_cloud_cpp_development)
+google_cloud_cpp_install_headers(google_cloud_cpp_pubsub_mocks
+                                 "include/google/cloud/pubsub")
 
 google_cloud_cpp_add_pkgconfig(
     pubsub