build: Print some configuration that is confusing me.

GNUmakefile

@@ -70,6 +70,14 @@ else
 $(error Unexpected host platform $(UNAME_S).)
 endif
 
+# Everything is set above.
+$(info VERSION_NUMBER = $(VERSION_NUMBER))
+$(info HAVE_ANDROID = $(HAVE_ANDROID))
+$(info HAVE_WIN = $(HAVE_WIN))
+$(info HAVE_CROSS_AARCH64 = $(HAVE_CROSS_AARCH64))
+$(info HAVE_LINUX_IOS = $(HAVE_LINUX_IOS))
+$(info USE_SYSTEM_SSL = $(USE_SYSTEM_SSL))
+
 CFLAGS += \
 	-std=gnu11 \
 	-Wall \