According to

http://www.astro.gla.ac.uk/~norman/star/dev-nxg-20040116-add-fpp-support/automake.html/Conditional-Subdirectories.html
All directories should be configured (i.e. Makefile generated) even if they aren't being built.
So we need to mark some intermediate sources (those built by Qt's machinery) as
part of sources but not as part of dist.

Makefile.am

@@ -22,7 +22,7 @@ install-data-local:
 	find "$(PRESETSDIR)" -type f -exec $(INSTALL_DATA) {} $(pm_presets_dir) \;
 
 # from https://stackoverflow.com/questions/30897170/ac-subst-does-not-expand-variable answer: https://stackoverflow.com/a/30960268
-# ptomato https://stackoverflow.com/users/172999/ptomato 
+# ptomato https://stackoverflow.com/users/172999/ptomato
 
 src/libprojectM/config.inp: src/libprojectM/config.inp.in Makefile
 	$(AM_V_GEN)rm -f $@ $@.tmp && \

configure.ac

@@ -20,6 +20,9 @@ AC_CONFIG_FILES([
   src/libprojectM/NativePresetFactory/Makefile
   src/libprojectM/MilkdropPresetFactory/Makefile
   src/NativePresets/Makefile
+  src/projectM-sdl/Makefile
+  src/projectM-qt/Makefile
+  src/projectM-pulseaudio/Makefile
 ])
 
 dnl SDL
@@ -31,7 +34,6 @@ AS_IF([test "x$enable_sdl" = "xyes"], [
   SDL_VERSION=2.0.5
   AS_IF([test "$TRAVIS"], [SDL_VERSION=2.0.2])  # travis has old SDL, we don't care
   AM_PATH_SDL2($SDL_VERSION, :, AC_MSG_ERROR([*** SDL version $SDL_VERSION not found!]))
-  AC_CONFIG_FILES([src/projectM-sdl/Makefile])
 ])
 
 dnl from https://stackoverflow.com/questions/30897170/ac-subst-does-not-expand-variable answer: https://stackoverflow.com/a/30960268
@@ -64,8 +66,6 @@ AS_IF([test "x$enable_qt" = "xyes"], [
   if test -z "$MOC" || test -z "$UIC" || test -z "$RCC"; then
     AC_MSG_ERROR([Qt utility programs moc, uic, and rcc are required.])
   fi
-  AC_CONFIG_FILES([src/projectM-qt/Makefile])
-  AC_CONFIG_FILES([src/projectM-pulseaudio/Makefile])
 
   PKG_CHECK_MODULES(LIBPULSE, [libpulse], [], [AC_MSG_ERROR([Pulseaudio library libpulse is required.])])
 ])
@@ -115,7 +115,7 @@ ldflags:                ${LDFLAGS}
 Applications:
 =====
 
-libprojectM:            Yes
+libprojectM:            yes
 SDL:                    ${enable_sdl}
 Qt & Pulseaudio:        ${enable_qt}
 ])

src/projectM-pulseaudio/Makefile.am

@@ -5,7 +5,7 @@ projectM_pulseaudio_qtheaders = \
 	QPulseAudioDeviceModel.hpp \
 	QPulseAudioThread.hpp
 
-projectM_pulseaudio_moc_sources = $(projectM_pulseaudio_qtheaders:.hpp=_moc.cpp)
+nodist_projectM_pulseaudio_moc_sources = $(projectM_pulseaudio_qtheaders:.hpp=_moc.cpp)
 
 .hpp_moc.cpp:
 	@MOC@ -o$@ $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(CPPFLAGS) $(MOC_CPPFLAGS)\

src/projectM-qt/Makefile.am

@@ -11,7 +11,7 @@ projectM_qt_qtheaders = qprojectm_mainwindow.hpp \
 	qprojectm.hpp \
 	qprojectmwidget.hpp
 
-projectM_qt_moc_sources = $(projectM_qt_qtheaders:.hpp=_moc.cpp)
+nodist_projectM_qt_moc_sources = $(projectM_qt_qtheaders:.hpp=_moc.cpp)
 
 .hpp_moc.cpp:
 	@MOC@ -o$@ $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(CPPFLAGS) $(MOC_CPPFLAGS)\
@@ -19,10 +19,10 @@ projectM_qt_moc_sources = $(projectM_qt_qtheaders:.hpp=_moc.cpp)
 
 ui_qprojectm_mainwindow.h: qprojectm_mainwindow.ui
 	@UIC@ -o $@ $<
-	
+
 ui_qpreseteditordialog.h: qpreseteditordialog.ui
 	@UIC@ -o $@ $<
-	
+
 ui_qprojectmconfigdialog.h: qprojectmconfigdialog.ui
 	@UIC@ -o $@ $<
 
@@ -45,11 +45,12 @@ libprojectM_qt_a_SOURCES = \
 	qplaylistmodel.cpp \
 	qprojectmconfigdialog.cpp \
 	qpresettextedit.cpp \
-	qpreseteditordialog.cpp \
+	qpreseteditordialog.cpp
+
+nodist_libprojectM_qt_a_SOURCES = \
 	application_qrc.cpp \
 	$(test_moc_sources)
 
-
 AM_CPPFLAGS = \
 	-include $(top_builddir)/config.h \
 	-DSYSCONFDIR=\""$(sysconfdir)"\" \
@@ -62,7 +63,7 @@ AM_CFLAGS = ${my_CFLAGS} \
 	-fvisibility=hidden \
 	-ffunction-sections \
 	-fdata-sections
-	
+
 CLEANFILES = \
 	application_qrc.cpp \
 	${BUILT_SOURCES} \