--- a/Makefile.in	Wed Mar 16 18:35:23 2022 +0800
+++ b/Makefile.in	Tue Mar 22 16:17:47 2022 +0800
@@ -20,13 +20,13 @@
 ifeq (@BUNDLED_LIBTOM@, 1)
 LIBTOM_DEPS=$(STATIC_LTC) $(STATIC_LTM) 
 LIBTOM_CLEAN=ltc-clean ltm-clean
-CFLAGS+=-I$(srcdir)/libtomcrypt/src/headers/
+CPPFLAGS+=-I$(srcdir)/libtomcrypt/src/headers/
 LIBTOM_LIBS=$(STATIC_LTC) $(STATIC_LTM)
 endif
 
 OPTION_HEADERS = default_options_guard.h sysoptions.h
 ifneq ($(wildcard localoptions.h),)
-CFLAGS+=-DLOCALOPTIONS_H_EXISTS
+CPPFLAGS+=-DLOCALOPTIONS_H_EXISTS
 OPTION_HEADERS += localoptions.h
 endif
 
@@ -107,8 +107,8 @@
 RANLIB=@RANLIB@
 STRIP=@STRIP@
 INSTALL=@INSTALL@
-CPPFLAGS=@CPPFLAGS@
-CFLAGS+=-I. -I$(srcdir) $(CPPFLAGS) @CFLAGS@
+CPPFLAGS+=@CPPFLAGS@ -I. -I$(srcdir)
+CFLAGS+=@CFLAGS@
 LIBS+=@LIBS@
 LDFLAGS=@LDFLAGS@
 
@@ -119,15 +119,16 @@
 # whether we're building client, server, or both for the common objects.
 # evilness so we detect 'dropbear' by itself as a word
 ifneq (,$(strip $(foreach prog, $(PROGRAMS), $(findstring ZdropbearZ, Z$(prog)Z))))
-	CFLAGS+= -DDROPBEAR_SERVER
+	CPPFLAGS+= -DDROPBEAR_SERVER
 endif
 ifneq (,$(strip $(foreach prog, $(PROGRAMS), $(findstring ZdbclientZ, Z$(prog)Z))))
-	CFLAGS+= -DDROPBEAR_CLIENT
+	CPPFLAGS+= -DDROPBEAR_CLIENT
 endif
 
 # these are exported so that libtomcrypt's makefile will use them
 export CC
 export CFLAGS
+export CPPFLAGS
 export RANLIB AR STRIP
 
 ifeq ($(STATIC), 1)
@@ -142,7 +143,7 @@
 
 # for the scp progress meter. The -D doesn't affect anything else.
 ifeq ($(SCPPROGRESS), 1)
-	CFLAGS+=-DPROGRESS_METER
+	CPPFLAGS+=-DPROGRESS_METER
 endif
 
 all: $(TARGETS)
@@ -216,7 +217,7 @@
 MULTIOBJS=
 ifeq ($(MULTI),1)
 	MULTIOBJS=dbmulti.o $(sort $(foreach prog, $(PROGRAMS), $($(prog)objs)))
-	CFLAGS+=$(addprefix -DDBMULTI_, $(PROGRAMS)) -DDROPBEAR_MULTI
+	CPPFLAGS+=$(addprefix -DDBMULTI_, $(PROGRAMS)) -DDROPBEAR_MULTI
 endif
 
 dropbearmulti$(EXEEXT): $(HEADERS) $(MULTIOBJS) $(LIBTOM_DEPS) Makefile

--- a/libtomcrypt/Makefile.in	Wed Mar 16 18:35:23 2022 +0800
+++ b/libtomcrypt/Makefile.in	Tue Mar 22 16:17:47 2022 +0800
@@ -42,7 +42,7 @@
 EXTRALIBS = ../libtommath/libtommath.a
 
 #Compilation flags
-LTC_CFLAGS  = -Isrc/headers/ -I$(srcdir)/src/headers/ -I../ -I$(srcdir)/../ -DLTC_SOURCE -I../libtommath/ -I$(srcdir)/../libtommath/ $(CFLAGS)
+LTC_CFLAGS  = -Isrc/headers/ -I$(srcdir)/src/headers/ -I../ -I$(srcdir)/../ -DLTC_SOURCE -I../libtommath/ -I$(srcdir)/../libtommath/ $(CFLAGS) $(CPPFLAGS)
 LTC_LDFLAGS = $(LDFLAGS) $(EXTRALIBS)
 VERSION=1.18.1
 

--- a/libtommath/Makefile.in	Wed Mar 16 18:35:23 2022 +0800
+++ b/libtommath/Makefile.in	Tue Mar 22 16:17:47 2022 +0800
@@ -8,6 +8,7 @@
 # So that libtommath can include Dropbear headers for options and m_burn()
 CFLAGS += -I$(srcdir) -I../libtomcrypt/src/headers/ -I$(srcdir)/../libtomcrypt/src/headers/ -I../ -I$(srcdir)/../
 CFLAGS += -Wno-deprecated
+CFLAGS += $(CPPFLAGS)
 
 V = 1