build: Install headers

Reintroduce this feature after 99ec371

It was useful for debian packaging (iotjs-dev),
to match quality standards.

Email has been updated for community support

Relate-to: https://packages.qa.debian.org/i/iotjs.html
Fowarded: jerryscript-project#1896
Relate-to: jerryscript-project#1145
Change-Id: Idd9a18bbe692baeb468152df5149374512e9350b
Bug: jerryscript-project#1945
IoT.js-DCO-1.0-Signed-off-by: Philippe Coval rzr@users.sf.net

cmake/iotjs.cmake

@@ -495,6 +495,12 @@ set(IOTJS_PUBLIC_HEADERS
   ${LIBUV_HEADERS}
 )
 
+# Install headers
+if("${INCLUDE_INSTALL_DIR}" STREQUAL "")
+  set(INCLUDE_INSTALL_DIR "include/iotjs")
+endif()
+install(FILES ${IOTJS_PUBLIC_HEADERS} DESTINATION ${INCLUDE_INSTALL_DIR})
+
 # Configure the libiotjs
 set(TARGET_LIB_IOTJS libiotjs)
 # Configure the libiotjs.a