Cmake add separate export for plugin targets (#31525)

* cmake: add separate export for plugin targets

Add a separate CMake export for the plugin targets to separate binaries
and libraries into their own CMake target export files. Skip the cross
compiled binary plugin targets during cross compile because they are not
usable and not always available.

The Yocto build system doesn't install cross compiled binaries into the
target sysroot. This makes the CMake gRPC config useless as it checks
the existent of binaries and fails without the binaries.

This is a strip down version of #22498 and related to #26148 and #26857.

Signed-off-by: Stefan Herbrechtsmeier <stefan.herbrechtsmeier@weidmueller.com>
Signed-off-by: Clément Péron <peron.clem@gmail.com>

* regenerate cmake file

Signed-off-by: Stefan Herbrechtsmeier <stefan.herbrechtsmeier@weidmueller.com>
Signed-off-by: Clément Péron <peron.clem@gmail.com>
Co-authored-by: Stefan Herbrechtsmeier <stefan.herbrechtsmeier@weidmueller.com>

cmake/gRPCConfig.cmake.in

@@ -11,3 +11,6 @@ list(APPEND CMAKE_MODULE_PATH ${CMAKE_CURRENT_LIST_DIR}/modules)
 
 # Targets
 include(${CMAKE_CURRENT_LIST_DIR}/gRPCTargets.cmake)
+if(NOT CMAKE_CROSSCOMPILING)
+  include(${CMAKE_CURRENT_LIST_DIR}/gRPCPluginTargets.cmake)
+endif()

templates/CMakeLists.txt.template

@@ -801,7 +801,11 @@
   % else:
   if(gRPC_INSTALL)
   % endif
+  % if tgt.build == 'protoc' and 'grpc_plugin_support' in tgt.get('deps', []):
+    install(TARGETS ${tgt.name} EXPORT gRPCPluginTargets
+  % else:
     install(TARGETS ${tgt.name} EXPORT gRPCTargets
+  % endif
       RUNTIME DESTINATION <%text>${gRPC_INSTALL_BINDIR}</%text>
       BUNDLE DESTINATION  <%text>${gRPC_INSTALL_BINDIR}</%text>
       LIBRARY DESTINATION <%text>${gRPC_INSTALL_LIBDIR}</%text>
@@ -815,6 +819,10 @@
       DESTINATION <%text>${gRPC_INSTALL_CMAKEDIR}</%text>
       NAMESPACE gRPC::
     )
+    install(EXPORT gRPCPluginTargets
+      DESTINATION <%text>${gRPC_INSTALL_CMAKEDIR}</%text>
+      NAMESPACE gRPC::
+    )
   endif()
 
   include(CMakePackageConfigHelpers)