https://bugs.gentoo.org/437992
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -4,5 +4,5 @@
 	        boss.h extern.h ranking.h your.h game.h\
 	        geki2.h load.h opening.h my.h misc.h
 
-CFLAGS = @X_CFLAGS@ @KXL_CFLAGS@
+AM_CFLAGS = @X_CFLAGS@ @KXL_CFLAGS@
 LIBS = @X_LIBS@ -lX11 @KXL_LIBS@ -lKXL