Add signing of px4 binary into makefiles

When an environment variable "SIGNING_TOOL" is defined, the make will
call this with two filename arguments: <input> and <output>.

The SIGNING_TOOL will read in the binary from input, and append
signature to the output. For example:

SIGNING_TOOL=${PWD}/Tools/cryptotools.py make px4_fmu-v5_default

Will use the example "cryptotools.py" to sign the px4_fmu-v5.bin

Signed-off-by: Jukka Laitinen <jukkax@ssrc.tii.ae>

platforms/nuttx/CMakeLists.txt

@@ -148,8 +148,20 @@ if (config_romfs_root)
 	target_link_libraries(px4 PRIVATE romfs)
 endif()
 
-add_custom_command(OUTPUT ${PX4_BINARY_DIR_REL}/${PX4_BOARD}.bin
-	COMMAND ${CMAKE_OBJCOPY} -O binary ${PX4_BINARY_DIR_REL}/${FW_NAME} ${PX4_BINARY_DIR_REL}/${PX4_BOARD}.bin
+if((DEFINED ENV{SIGNING_TOOL}) AND (NOT NUTTX_DIR MATCHES "external"))
+	set(PX4_BINARY_OUTPUT ${PX4_BINARY_DIR}/${PX4_BOARD}_unsigned.bin)
+
+	add_custom_command(OUTPUT ${PX4_BINARY_DIR_REL}/${PX4_BOARD}.bin
+		COMMAND $ENV{SIGNING_TOOL} $ENV{SIGNING_ARGS} ${PX4_BINARY_OUTPUT} ${PX4_BINARY_DIR}/${PX4_BOARD}.bin
+		DEPENDS ${PX4_BINARY_OUTPUT}
+		WORKING_DIRECTORY ${PX4_SOURCE_DIR}
+)
+else()
+set(PX4_BINARY_OUTPUT ${PX4_BINARY_DIR_REL}/${PX4_BOARD}.bin)
+endif()
+
+add_custom_command(OUTPUT ${PX4_BINARY_OUTPUT}
+	COMMAND ${CMAKE_OBJCOPY} -O binary ${PX4_BINARY_DIR_REL}/${FW_NAME} ${PX4_BINARY_OUTPUT}
 	DEPENDS px4
 	)