diff -Naur free42-nologo-2.5.16.orig/gtk/Makefile free42-nologo-2.5.16/gtk/Makefile
--- free42-nologo-2.5.16.orig/gtk/Makefile	2020-01-25 05:16:45.000000000 +0100
+++ free42-nologo-2.5.16/gtk/Makefile	2020-02-02 20:18:50.460458652 +0100
@@ -15,7 +15,7 @@
 # along with this program; if not, see http://www.gnu.org/licenses/.
 ###############################################################################
 
-CFLAGS = -MMD \
+CFLAGS := -MMD \
 	 -Wall \
 	 -Wno-parentheses \
 	 -Wno-write-strings \
@@ -34,12 +34,14 @@
 	 -DDECIMAL_GLOBAL_ROUNDING=1 \
 	 -DDECIMAL_GLOBAL_ROUNDING_ACCESS_FUNCTIONS=1 \
 	 -DDECIMAL_GLOBAL_EXCEPTION_FLAGS=1 \
-	 -DDECIMAL_GLOBAL_EXCEPTION_FLAGS_ACCESS_FUNCTIONS=1
+	 -DDECIMAL_GLOBAL_EXCEPTION_FLAGS_ACCESS_FUNCTIONS=1 \
+	 ${CFLAGS}
 
-CXXFLAGS = $(CFLAGS) \
+CXXFLAGS := $(CFLAGS) \
 	 -fno-exceptions \
 	 -fno-rtti \
-	 -D_WCHAR_T_DEFINED
+	 -D_WCHAR_T_DEFINED \
+	 ${CXXFLAGS}
 
 LIBS = gcc111libbid.a $(shell pkg-config --libs gtk+-3.0)
 
@@ -114,7 +116,7 @@
 	./keymap2cc
 
 gcc111libbid.a:
-	sh ./build-intel-lib.sh
+	+sh ./build-intel-lib.sh
 	ln -s IntelRDFPMathLib20U1/TESTS/readtest.c
 
 symlinks: