Properly handle JEMALLOC_* Autoconf variables

The AX_CHECK_JEMALLOC() m4 macro sets the JEMALLOC_CFLAGS variable, not
JEMALLOC_CPPFLAGS.  Furthermore, the JEMALLOC_CFLAGS and JEMALLOC_LIBS
variables should only be included in the build flags if jemalloc was
successfully configured.  Tweak lib/isc/Makefile.am accordingly.

configure.ac

@@ -1338,6 +1338,8 @@ AS_CASE([$with_jemalloc],
 AS_IF([test "$with_jemalloc" = "no"],
       [AC_CHECK_FUNCS([malloc_size malloc_usable_size])])
 
+AM_CONDITIONAL([HAVE_JEMALLOC], [test "$with_jemalloc" = "yes"])
+
 #
 # was --with-tuning specified?
 #

lib/isc/Makefile.am

@@ -212,7 +212,6 @@ libisc_la_SOURCES =		\
 
 libisc_la_CPPFLAGS =		\
 	$(AM_CPPFLAGS)		\
-	$(JEMALLOC_CPPFLAGS)	\
 	$(LIBISC_CFLAGS)	\
 	$(LIBUV_CFLAGS)		\
 	$(OPENSSL_CFLAGS)	\
@@ -223,11 +222,26 @@ libisc_la_LDFLAGS =		\
 	-release "$(PACKAGE_VERSION)"
 
 libisc_la_LIBADD =		\
-	$(JEMALLOC_LIBS)	\
 	$(LIBUV_LIBS)		\
 	$(OPENSSL_LIBS)		\
 	$(ZLIB_LIBS)
 
+if HAVE_JEMALLOC
+libisc_la_CPPFLAGS +=		\
+	$(JEMALLOC_CFLAGS)
+
+libisc_la_LIBADD +=		\
+	$(JEMALLOC_LIBS)
+endif HAVE_JEMALLOC
+
+if HAVE_JSON_C
+libisc_la_CPPFLAGS +=		\
+	$(JSON_C_CFLAGS)
+
+libisc_la_LIBADD +=		\
+	$(JSON_C_LIBS)
+endif HAVE_JSON_C
+
 if HAVE_LIBNGHTTP2
 libisc_la_SOURCES +=		\
 	netmgr/http.c		\
@@ -240,14 +254,6 @@ libisc_la_LIBADD +=		\
 	$(LIBNGHTTP2_LIBS)
 endif
 
-if HAVE_JSON_C
-libisc_la_CPPFLAGS +=		\
-	$(JSON_C_CFLAGS)
-
-libisc_la_LIBADD +=		\
-	$(JSON_C_LIBS)
-endif HAVE_JSON_C
-
 if HAVE_LIBXML2
 libisc_la_CPPFLAGS +=		\
 	$(LIBXML2_CFLAGS)