Makefile tree for debug/test/release builds with multiple targets - makefile

Question

Structure:
makefile
system/
-> makefile
-> kernel/
-> -> makefile
-> -> src/
-> FutureModules
-> -> makefile
-> -> src/
userland/
-> makefile
-> FutureModules
-> -> makefile
-> -> src/
Currently I'm building it with make system.
I'd like to split it up into Debug/Test/Release builds so that i can do something like make debug system or make -d system with multiple targets (e.g. make debug system userland or something like that).
I'd like to change the targets so i can directly build a target instead of building system and manually have to add the desired targets in system/makefile.
Now in order to achieve this:
Do constants get shared between makefiles? So when i do make system and i define CFLAGS += -g -Og in the root makefile, does the system/makefile get the constants from the root makefile?
Do constants stay the same in a make session? So when i do make debug system userland and have something like debug: CFLAGS += -g -Og, do system and userland get the -g -Og flags?
EDIT: I managed to achieve 2. by using $(shell find -maxdepth 1 -type d) and some other commands.

Answer 1

Solved it with:
#Build mode. m=d => Debug | m=t => Test | m=r => release | default => release
ifeq ($(m), d)
NASBUILD = $(NASDEBUG)
GASBUILD = $(GASDEBUG)
CPPBUILD = $(CPPDEBUG)
CBUILD = $(CDEBUG)
else ifeq ($(m), t)
NASBUILD = $(NASTEST)
GASBUILD = $(GASTEST)
CPPBUILD = $(CPPTEST)
CBUILD = $(CTEST)
else ifeq ($(m), r)
NASBUILD = $(NASRELEASE)
GASBUILD = $(GASRELEASE)
CPPBUILD = $(CPPRELEASE)
CBUILD = $(CRELEASE)
else
NASBUILD = $(NASRELEASE)
GASBUILD = $(GASRELEASE)
CPPBUILD = $(CPPRELEASE)
CBUILD = $(CRELEASE)
endif
export NASBUILD
export GASBUILD
export CPPBUILD
export CBUILD
Where xxxBUILD and so on gets added to the corresponding xxxFLAGS.