The goal is to only execute recipes when there is an actual change in
the prerequisites.
There are several issues which cause the nuttx binary target to be
re-made every time the top level make is run.
1. Previously the target nuttx$(EXEEXT), was used, but make resolved
this in the relative directory make -C $(ARCH_SRC), and couldn’t find
it (need an absolute path: `$(TOPDIR)/..).
2. The .tmp prerequisite for nuttx was always deleted
3. libboard's recipe had a sub-make which may or may not update that
target. This was a phony target, and was therefore always considered out
of date.
These issues were causing the nuttx recipe to be run every make, which
was hiding some missing prerequisites:
1. the .config is a prerequisite for the .tmp target
2. libapps.a (and other linklibs) are pre-requisites for nuttx
Changes:
The changes are only in the build system, and only for arm.
Track nuttx$(EXEEXT) via vpath so Make knows when it's already up to
date without an explicit path. Add $(TOPDIR)/.config as a dependency
to the linker script preprocessing so config changes trigger
re-preprocessing.
Keep the .tmp linker script on disk (clean already removes it) so
timestamp-based dependency checking works across builds. These .tmp
files need to be added to the gitignore or the CI will complain.
Use FORCE pattern for board/libboard to ensure it's always checked
but use the actual library file as the link dependency so nuttx is
only re-linked when library content changes. Add staging libs as
dependency to nuttx link rule so changed app libs trigger re-link.
Signed-off-by: Liam Hickey <williamhickey@geotab.com>
13ba91a33f