Add Stdexec to HPXConfig

cmake/templates/HPXConfig.cmake.in

@@ -27,6 +27,18 @@ else()
   include(HPX_SetupAsio)
 endif()
 
+
+# Stdexec can be installed by HPX or externally installed. In the first case we use
+# exported targets, in the second we find Stdexec again using find_package.
+if(HPX_WITH_FETCH_STDEXEC)
+  include("${CMAKE_CURRENT_LIST_DIR}/HPXStdexecTarget.cmake")
+else()
+  set(Stdexec_ROOT "@Stdexec_ROOT@")
+  include(HPX_SetupStdexec)
+endif()
+
+
+
 # NLohnmann JSON can be installed by HPX or externally installed. In the first
 # case we use exported targets, in the second we find JSON again using
 # find_package.