Globally configurable stack checks, R10 is always fixed

nuttx-configs/px4fmu-v2/nsh/Make.defs

@@ -62,8 +62,14 @@ ARCHCPUFLAGS		 = -mcpu=cortex-m4 \
 
 
 # enable precise stack overflow tracking
+ENABLE_STACK_CHECKS ?= 0
+ifneq ($(ENABLE_STACK_CHECKS),0)
+$(info Stack checks enabled)
 INSTRUMENTATIONDEFINES	 = -finstrument-functions \
 			   -ffixed-r10
+else
+INSTRUMENTATIONDEFINES	 = -ffixed-r10
+endif
 
 # pull in *just* libm from the toolchain ... this is grody
 LIBM			 = "${shell $(CC) $(ARCHCPUFLAGS) -print-file-name=libm.a}"