terminal: only build if --enable-terminal was specified

Whoopsy, I totally forgot adding the "if ENABLE_TERMINAL" markers. Do that
now that we know it builds fine everywhere.

Makefile.am

@@ -2831,9 +2831,18 @@ tests += \
 	test-dhcp6-client
 
 # ------------------------------------------------------------------------------
+if ENABLE_TERMINAL
 noinst_LTLIBRARIES += \
 	libsystemd-terminal.la
 
+noinst_PROGRAMS += \
+	systemd-subterm
+
+tests += \
+	test-term-page \
+	test-term-parser
+endif
+
 libsystemd_terminal_la_CFLAGS = \
 	$(AM_CFLAGS)
 
@@ -2849,9 +2858,6 @@ libsystemd_terminal_la_LIBADD = \
 	libsystemd-internal.la \
 	libsystemd-shared.la
 
-noinst_PROGRAMS += \
-	systemd-subterm
-
 systemd_subterm_SOURCES = \
 	src/libsystemd-terminal/subterm.c
 
@@ -2876,10 +2882,6 @@ test_term_parser_LDADD = \
 	libsystemd-internal.la \
 	libsystemd-shared.la
 
-tests += \
-	test-term-page \
-	test-term-parser
-
 # ------------------------------------------------------------------------------
 if ENABLE_GTK_DOC
 SUBDIRS += \