cmake/macros: use in-build capnp tools if capnroto is built in cmake

If CapnProto is part of cmake build, macro CAPNP_GENERATE_CPP
uses in-build capnp tools.

This change fixes `make check` target with cmake.

All tests pass except
1: [ FAIL ] exception-test.c++:30: legacy test:
    Exception/TrimSourceFilename
1: /home/brano/src/capnproto/c++/src/kj/exception-test.c++:31:
    failed: expected (trimSourceFilename(
    "/home/brano/src/capnproto/c++/src/kj/exception-test.c++"))
    == ("kj/exception-test.c++");

Not sure how to fix the test without disabling it.

c++/cmake/CapnProtoMacros.cmake

@@ -26,6 +26,14 @@ function(CAPNP_GENERATE_CPP SOURCES HEADERS)
   if(NOT ARGN)
     message(SEND_ERROR "CAPNP_GENERATE_CPP() called without any source files.")
   endif()
+  set(tool_depends ${EMPTY_STRING})
+  #Use cmake targets available
+  if(TARGET capnp_tool)
+    set(CAPNP_EXECUTABLE capnp_tool)
+    GET_TARGET_PROPERTY(CAPNPC_CXX_EXECUTABLE capnpc_cpp CAPNPC_CXX_EXECUTABLE)
+    GET_TARGET_PROPERTY(CAPNP_INCLUDE_DIRECTORY capnp_tool CAPNP_INCLUDE_DIRECTORY)
+    list(APPEND tool_depends capnp_tool capnpc_cpp)
+  endif()
   if(NOT CAPNP_EXECUTABLE)
     message(SEND_ERROR "Could not locate capnp executable (CAPNP_EXECUTABLE).")
   endif()
@@ -92,7 +100,7 @@ function(CAPNP_GENERATE_CPP SOURCES HEADERS)
           ${include_path}
           ${CAPNPC_FLAGS}
           ${file_path}
-      DEPENDS "${schema_file}"
+      DEPENDS "${schema_file}" ${tool_depends}
       COMMENT "Compiling Cap'n Proto schema ${schema_file}"
       VERBATIM
     )

c++/src/capnp/CMakeLists.txt

@@ -143,12 +143,20 @@ if(BUILD_TOOLS AND NOT CAPNP_LITE)
   )
   target_link_libraries(capnp_tool capnpc capnp kj)
   set_target_properties(capnp_tool PROPERTIES OUTPUT_NAME capnp)
+  set_target_properties(capnp_tool PROPERTIES CAPNP_INCLUDE_DIRECTORY
+    $<JOIN:$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/..>,$<INSTALL_INTERFACE:${CMAKE_INSTALL_BINDIR}/..>>
+  )
 
   add_executable(capnpc_cpp
     compiler/capnpc-c++.c++
   )
   target_link_libraries(capnpc_cpp capnp kj)
   set_target_properties(capnpc_cpp PROPERTIES OUTPUT_NAME capnpc-c++)
+  #Capnp tool needs capnpc_cpp location. But cmake deprecated LOCATION property.
+  #So we use custom property to pass location
+  set_target_properties(capnpc_cpp PROPERTIES CAPNPC_CXX_EXECUTABLE
+    $<JOIN:$<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/capnpc-c++>,$<INSTALL_INTERFACE:${CMAKE_INSTALL_BINDIR}/capnpc-c++>>
+  )
 
   add_executable(capnpc_capnp
     compiler/capnpc-capnp.c++