Add missing installdir

src/syncterm/GNUmakefile

@@ -51,6 +51,7 @@ installdirs:
 	-mkdir -p ${PREFIX}/bin
 	-mkdir -p ${PREFIX}/share/applications
 	-mkdir -p ${PREFIX}/share/man/man1
+	-mkdir -p ${PREFIX}/share/icons/hicolor/64x64/apps
 
 install: $(SYNCTERM) syncterm.1.gz installdirs
 	@echo Installing...