Change CMAKE_SYSROOT to use CACHE PATH

Author: pablorcum

toolbox/overlay-triplets/qnx-toolchain.cmake

@@ -40,7 +40,7 @@ set(CMAKE_CXX_COMPILER_TARGET ${QNX_QCC_VARIANT})
 #   $QNX_TARGET/aarch64le
 #   $QNX_TARGET/armle-v7
 #   $QNX_TARGET/x86_64
-set(CMAKE_SYSROOT "$ENV{QNX_TARGET}" )
+set(CMAKE_SYSROOT "$ENV{QNX_TARGET}" CACHE PATH "")
 set(CMAKE_FIND_ROOT_PATH "${CMAKE_SYSROOT}" CACHE PATH "")
 set(CMAKE_PREFIX_PATH ${CMAKE_SYSROOT}/${QNX_SYSROOT_SUFFIX}; ${CMAKE_SYSROOT}/${QNX_SYSROOT_SUFFIX}/usr)