cmake: Remove global include of board dir

Remove having ${BOARD_DIR} in the global include path for Zephyr builds.
Needed to add this to the arch/posix because of how posix "boards"
define various things like interrupt handling.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>

CMakeLists.txt

@@ -53,7 +53,6 @@ zephyr_include_directories(
   ${SOC_DIR}/${ARCH}/${SOC_PATH}
   ${SOC_DIR}/${ARCH}/${SOC_PATH}/include
   ${SOC_DIR}/${ARCH}/${SOC_FAMILY}/include
-  ${BOARD_DIR}
   include
   include/drivers
   ${PROJECT_BINARY_DIR}/include/generated

arch/posix/CMakeLists.txt

@@ -9,6 +9,8 @@ zephyr_compile_options(
   -include ${ZEPHYR_BASE}/arch/posix/include/posix_cheats.h
   )
 
+zephyr_include_directories(${BOARD_DIR})
+
 zephyr_compile_options_ifdef(CONFIG_COVERAGE
   -fprofile-arcs
   -ftest-coverage