Pango now requires harfbuzz, but it's not searched for.

--- cmake/Modules/FindGTK3.cmake
+++ cmake/Modules/FindGTK3.cmake
@@ -60,6 +60,21 @@ if(NOT GLIB2_FOUND)
 	set(_GTK3_found_all false)
 endif()
 
+# Harfbuzz
+
+pkg_check_modules(PC_HARFBUZZ harfbuzz)
+
+if(NOT PC_HARFBUZZ_FOUND)
+	set(_GTK3_found_all false)
+endif()
+
+find_path(HARFBUZZ_INCLUDE_DIR hb.h
+        HINTS ${PC_HARFBUZZ_INCLUDEDIR} ${PC_HARFBUZZ_INCLUDE_DIRS}
+        PATH_SUFFIXES harfbuzz)
+
+find_library(HARFBUZZ_LIBRARY NAMES harfbuzz
+        HINTS ${PC_HARFBUZZ_LIBDIR} ${PC_HARFBUZZ_LIBRARY_DIRS})
+
 # Pango
 
 pkg_check_modules(PC_PANGO pango)
@@ -108,8 +123,8 @@ if(_GTK3_found_all)
 
 	find_package_handle_standard_args(GTK3 DEFAULT_MSG GTK3_LIBRARY GTK3_INCLUDE_DIR)
 
-	set(GTK3_LIBRARIES ${GTK3_LIBRARY} ${GDK3_LIBRARY} ${GLIB2_LIBRARIES} ${PANGO_LIBRARY} ${CAIRO_LIBRARY} ${GDKPIXBUF_LIBRARY} ${ATK_LIBRARY})
-	set(GTK3_INCLUDE_DIRS ${GTK3_INCLUDE_DIR} ${GLIB2_INCLUDE_DIRS} ${PANGO_INCLUDE_DIR} ${CAIRO_INCLUDE_DIR} ${GDKPIXBUF_INCLUDE_DIR} ${ATK_INCLUDE_DIR})
+	set(GTK3_LIBRARIES ${GTK3_LIBRARY} ${GDK3_LIBRARY} ${GLIB2_LIBRARIES} ${HARFBUZZ_LIBRARY} ${PANGO_LIBRARY} ${CAIRO_LIBRARY} ${GDKPIXBUF_LIBRARY} ${ATK_LIBRARY})
+	set(GTK3_INCLUDE_DIRS ${GTK3_INCLUDE_DIR} ${GLIB2_INCLUDE_DIRS} ${HARFBUZZ_INCLUDE_DIR} ${PANGO_INCLUDE_DIR} ${CAIRO_INCLUDE_DIR} ${GDKPIXBUF_INCLUDE_DIR} ${ATK_INCLUDE_DIR})
 
 	mark_as_advanced(GTK3_INCLUDE_DIR GTK3_LIBRARY)