Fix: change libts to export a CMake package

libts install content was not compatible to find_module() which made
using a pre-built libts binary from CMake less than ideal.

This change adds the missing files and updates export and install
commands to make libts generate a proper CMake package.

From now on an external project will be able to use find_module() to
integrate libts into its build.

Signed-off-by: Gyorgy Szing <Gyorgy.Szing@arm.com>
Change-Id: I9e86e02030f6fb3c86af45252110f939cb82670c
diff --git a/components/messaging/ffa/libsp/component.cmake b/components/messaging/ffa/libsp/component.cmake
index a21c630..64e8814 100644
--- a/components/messaging/ffa/libsp/component.cmake
+++ b/components/messaging/ffa/libsp/component.cmake
@@ -1,5 +1,5 @@
 #-------------------------------------------------------------------------------
-# Copyright (c) 2020-2021, Arm Limited and Contributors. All rights reserved.
+# Copyright (c) 2020-2022, Arm Limited and Contributors. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -21,7 +21,7 @@
 	"${CMAKE_CURRENT_LIST_DIR}/sp_rxtx.c"
 	)
 
-set_property(TARGET ${TGT} PROPERTY PUBLIC_HEADER
+set_property(TARGET ${TGT} APPEND PROPERTY PUBLIC_HEADER
 	${CMAKE_CURRENT_LIST_DIR}/include/ffa_api.h
 	${CMAKE_CURRENT_LIST_DIR}/include/ffa_api_defines.h
 	${CMAKE_CURRENT_LIST_DIR}/include/ffa_api_types.h
@@ -49,5 +49,5 @@
 target_include_directories(${TGT}
 	 PUBLIC
 		"$<BUILD_INTERFACE:${CMAKE_CURRENT_LIST_DIR}/include>"
-		"$<INSTALL_INTERFACE:include>"
+		"$<INSTALL_INTERFACE:${TS_ENV}/include>"
 	)