Fix "make dist" without gobject

Cmake might need adjusting.
diff --git a/src/Makefile.am b/src/Makefile.am
index 1bf76c8..bb2c30e 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -212,13 +212,13 @@
 if HAVE_GOBJECT
 lib_LTLIBRARIES += libharfbuzz-gobject.la
 libharfbuzz_gobject_la_LINK = $(chosen_linker) $(libharfbuzz_gobject_la_LDFLAGS)
-libharfbuzz_gobject_la_SOURCES = $(HB_GOBJECT_sources)
+libharfbuzz_gobject_la_SOURCES = $(HB_GOBJECT_DIST_sources)
 libharfbuzz_gobject_la_CPPFLAGS = $(HBCFLAGS) $(HBNOLIBCXXFLAGS) $(GOBJECT_CFLAGS)
 libharfbuzz_gobject_la_LDFLAGS = $(base_link_flags)
 libharfbuzz_gobject_la_LIBADD = $(GOBJECT_LIBS) libharfbuzz.la
 EXTRA_libharfbuzz_gobject_la_DEPENDENCIES = $(harfbuzz_gobject_def_dependency)
-pkginclude_HEADERS += $(HB_GOBJECT_headers)
-nodist_pkginclude_HEADERS += $(HB_GOBJECT_ENUM_headers)
+pkginclude_HEADERS += $(HB_GOBJECT_DIST_headers)
+nodist_pkginclude_HEADERS += $(HB_GOBJECT_NODIST_headers)
 pkgconfig_DATA += harfbuzz-gobject.pc
 
 BUILT_SOURCES += \
diff --git a/src/Makefile.sources b/src/Makefile.sources
index 87fa807..bf07993 100644
--- a/src/Makefile.sources
+++ b/src/Makefile.sources
@@ -200,9 +200,9 @@
 	hb-subset-private.hh \
 	$(NULL)
 
-HB_GOBJECT_STRUCTS_sources = hb-gobject-structs.cc
-HB_GOBJECT_STRUCTS_headers = hb-gobject-structs.h
-HB_GOBJECT_ENUM_sources = hb-gobject-enums.cc
-HB_GOBJECT_ENUM_headers = hb-gobject-enums.h
-HB_GOBJECT_sources = $(HB_GOBJECT_STRUCTS_sources) $(HB_GOBJECT_ENUM_sources)
-HB_GOBJECT_headers = hb-gobject.h $(HB_GOBJECT_STRUCTS_headers) $(HB_GOBJECT_ENUM_headers)
+HB_GOBJECT_DIST_sources = hb-gobject-structs.cc
+HB_GOBJECT_DIST_headers = hb-gobject.h hb-gobject-structs.h
+HB_GOBJECT_NODIST_sources = hb-gobject-enums.cc
+HB_GOBJECT_NODIST_headers = hb-gobject-enums.h
+HB_GOBJECT_sources = $(HB_GOBJECT_DIST_sources) $(HB_GOBJECT_NODIST_sources)
+HB_GOBJECT_headers = $(HB_GOBJECT_DIST_headers) $(HB_GOBJECT_NODIST_headers)