build: Switch to non-recursive make

Build logic moves from individual Makefile.am's to include files, which
the main src/Makefile.am includes. This avoids having to manage a gigantic
single Makefile.

TODO: Move the rules from the old Makefile.include to where they actually
belong and nuke the old file.

src/Makefile.am

@@ -11,6 +11,7 @@ noinst_LIBRARIES += libbitcoin_wallet.a
 endif
 
 bin_PROGRAMS =
+TESTS =
 
 if BUILD_BITCOIND
   bin_PROGRAMS += bitcoind
@@ -20,8 +21,6 @@ if BUILD_BITCOIN_CLI
   bin_PROGRAMS += bitcoin-cli
 endif
 
-SUBDIRS = . $(BUILD_QT) $(BUILD_TEST)
-DIST_SUBDIRS = . qt test
 .PHONY: FORCE
 # bitcoin core #
 BITCOIN_CORE_H = \
@@ -188,16 +187,24 @@ leveldb/%.a:
 	  CC="$(CC)" PLATFORM=$(TARGET_OS) AR="$(AR)" $(LEVELDB_TARGET_FLAGS) \
 	  OPT="$(CXXFLAGS) $(CPPFLAGS)"
 
-qt/bitcoinstrings.cpp: $(libbitcoin_server_a_SOURCES) $(libbitcoin_common_a_SOURCES) $(libbitcoin_cli_a_SOURCES)
-	@test -n $(XGETTEXT) || echo "xgettext is required for updating translations"
-	@cd $(top_srcdir); XGETTEXT=$(XGETTEXT) share/qt/extract_strings_qt.py
-
 CLEANFILES = leveldb/libleveldb.a leveldb/libmemenv.a *.gcda *.gcno
 
 DISTCLEANFILES = obj/build.h
 
-EXTRA_DIST = leveldb Makefile.include
+EXTRA_DIST = leveldb
 
 clean-local:
 	-$(MAKE) -C leveldb clean
 	rm -f leveldb/*/*.gcno leveldb/helpers/memenv/*.gcno
+
+if ENABLE_TESTS
+include Makefile.test.include
+endif
+
+if ENABLE_QT
+include Makefile.qt.include
+endif
+
+if ENABLE_QT_TESTS
+include Makefile.qttest.include
+endif