cmake: Fixed openocd

Signed-off-by: Sebastian Boe <sebastian.boe@nordicsemi.no>
diff --git a/cmake/flash/CMakeLists.txt b/cmake/flash/CMakeLists.txt
index 4898fd0..a8a6bbb 100644
--- a/cmake/flash/CMakeLists.txt
+++ b/cmake/flash/CMakeLists.txt
@@ -6,7 +6,8 @@
   KERNEL_BIN_NAME=${KERNEL_BIN_NAME}
              ARCH=${ARCH}
        BOARD_NAME=${BOARD}
-             GDB=${CMAKE_GDB}
+              GDB=${CMAKE_GDB}
+          OPENOCD=${OPENOCD}
   )
 
 foreach(target flash debug debugserver)
diff --git a/cmake/host-tools.cmake b/cmake/host-tools.cmake
index 222cffa..43d5139 100644
--- a/cmake/host-tools.cmake
+++ b/cmake/host-tools.cmake
@@ -38,6 +38,12 @@
   mconf
   )
 
+# openocd is an optional dependency
+find_program(
+  OPENOCD
+  openocd
+  )
+
 # qemu is an optional dependency
 if("${ARCH}" STREQUAL "x86")
   set(QEMU_binary_suffix i386)