unify HOST_CFLAGS and HOSTCFLAGS

The top build system sets up HOSTCFLAGS a bit and exports it, but other
places use HOST_CFLAGS instead.  Unify the two as HOSTCFLAGS so that the
values stay in sync.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/tools/gdb/Makefile b/tools/gdb/Makefile
index c44cc8a..0a5687d 100644
--- a/tools/gdb/Makefile
+++ b/tools/gdb/Makefile
@@ -38,7 +38,7 @@
 # Use native tools and options
 #
 CPPFLAGS   = -I$(BFD_ROOT_DIR)/include
-CFLAGS     = $(HOST_CFLAGS) -O $(CPPFLAGS)
+CFLAGS     = $(HOSTCFLAGS) -O $(CPPFLAGS)
 CC	   = $(HOSTCC)
 MAKEDEPEND = makedepend