Hotfix: Disable instrumentation on IO

makefiles/toolchain_gnu-arm-eabi.mk

@@ -70,6 +70,14 @@ ARCHCPUFLAGS_CORTEXM3	 = -mcpu=cortex-m3 \
 			   -march=armv7-m \
 			   -mfloat-abi=soft
 
+ARCHINSTRUMENTATIONDEFINES_CORTEXM4F = -finstrument-functions \
+			   -ffixed-r10
+
+ARCHINSTRUMENTATIONDEFINES_CORTEXM4 = -finstrument-functions \
+			   -ffixed-r10
+
+ARCHINSTRUMENTATIONDEFINES_CORTEXM3 = 
+
 # Pick the right set of flags for the architecture.
 #
 ARCHCPUFLAGS		 = $(ARCHCPUFLAGS_$(CONFIG_ARCH))
@@ -91,8 +99,8 @@ ARCHOPTIMIZATION	 = $(MAXOPTIMIZATION) \
 
 # enable precise stack overflow tracking
 # note - requires corresponding support in NuttX
-INSTRUMENTATIONDEFINES	 = -finstrument-functions \
-			   -ffixed-r10
+INSTRUMENTATIONDEFINES	 = $(ARCHINSTRUMENTATIONDEFINES_$(CONFIG_ARCH))
+
 # Language-specific flags
 #
 ARCHCFLAGS		 = -std=gnu99