Can't easily disable doxygen use, use a bigger hammer.

Index: Makefile.am
--- Makefile.am.orig
+++ Makefile.am
@@ -1,4 +1,4 @@
-SUBDIRS = . include src test doc platform
+SUBDIRS = . include src test platform
 EXTRA_DIST = CHANGELOG.md README.md LICENSE
 
 pkgconfigdir = $(libdir)/pkgconfig
