build: Fix make distcheck

Change-Id: I1fa5e34b44331cd56408ea7ad4483dcf6443b259
diff --git a/Transceiver52M/arch/arm/Makefile.am b/Transceiver52M/arch/arm/Makefile.am
index 89ffb32..bc6da72 100644
--- a/Transceiver52M/arch/arm/Makefile.am
+++ b/Transceiver52M/arch/arm/Makefile.am
@@ -4,7 +4,7 @@
 ARCH_FLAGS = -mfpu=neon
 endif
 
-AM_CFLAGS = -Wall $(ARCH_FLAGS) -std=gnu99 -I../common
+AM_CFLAGS = -Wall $(ARCH_FLAGS) -std=gnu99 -I${srcdir}/../common
 AM_CCASFLAGS = $(ARCH_FLAGS)
 
 noinst_LTLIBRARIES = libarch.la