Cannot specify custom PSP directory using psp_MISSION_DIR

[astrogeco]

Describe the bug

Originally discussed in #1864 by @jbohren-hbr

Cannot specify "non-standard" psp source directory via the environment variable $CFS_APP_PATH or the cmake variable ${psp_SEARCH_PATH}.

The cFE cmake build infrastructure uses the environment / cmake variable $CFS_APP_PATH
as well as the cmake meta-variable pattern ${${APP}_SEARCH_PATH} to locate apps and other modules (such as psp), and subsequently sets the variable pattern ${${APP}_MISSION_DIR} (see mission_build.cmake lines 202-222).

cFE/cmake/mission_build.cmake

Lines 202 to 222 in 5e41330

	# Now search for the rest of CFS applications/libraries/modules - these may exist in
	# any directory within the search path.
	foreach(APP ${MISSION_DEPS})
	set (APPFOUND FALSE)
	foreach(APPSRC ${MISSION_MODULE_SEARCH_PATH} ${${APP}_SEARCH_PATH})
	if (NOT IS_ABSOLUTE "${APPSRC}")
	set(APPSRC "${MISSION_SOURCE_DIR}/${APPSRC}")
	endif()
	if(IS_DIRECTORY "${APPSRC}/${APP}")
	set(APPFOUND "${APPSRC}/${APP}")
	break()
	endif()
	endforeach()
	if (APPFOUND)
	get_filename_component(${APP}_MISSION_DIR "${APPFOUND}" ABSOLUTE)
	message(STATUS "Module '${APP}' found at ${${APP}_MISSION_DIR}")
	else()
	message("** Module ${APP} NOT found **")
	math(EXPR APP_MISSING_COUNT "${APP_MISSING_COUNT} + 1")
	endif()
	endforeach()

However, the resulting variable ${psp_MISSION_DIR} is not used in process_arch() in arch_build.cmake line 588 when including a target platform's build_options.cmake file. This causes a cmake configuration failure when trying to use a non-standard psp location.

cFE/cmake/arch_build.cmake

Lines 587 to 589 in 5e41330

	# Include any specific compiler flags or config from the selected PSP
	include(${MISSION_SOURCE_DIR}/psp/fsw/${CFE_SYSTEM_PSPNAME}/make/build_options.cmake)

To Reproduce
Build with psp in non-standard location, with the CFS_APP_PATH environment variable set

Expected behavior
${psp_MISSION_DIR} is used in process_arch() in arch_build.cmake for a successful build

System observed on:
System(s) tested on

Hardware: PC
OS: Ubuntu 18.04
Versions: cFE v6.8.0-rc1+dev933

Reporter Info
@jbohren-hbr

[jbohren-hbr]

@astrogeco thanks for retroactively creating the issue! This is all accurate.