build: add option for reducing exports (v2)

This was committed previously as 4975ae172 and reverted, because the flags were
applied even if the checks didn't pass. This is the same commit, fixed up to
actually disable the functionality when necessary.

Enabled automatically if boost >= 1.49.
See: https://svn.boost.org/trac/boost/ticket/2309

Also, check for a default visibility attribute, so that we can mark future
api functions correctly.

src/Makefile.am

@@ -261,6 +261,7 @@ endif
 
 bitcoind_LDADD += $(BOOST_LIBS) $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS)
 bitcoind_CPPFLAGS = $(BITCOIN_INCLUDES)
+bitcoind_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS)
 
 # bitcoin-cli binary #
 bitcoin_cli_LDADD = \
@@ -298,10 +299,12 @@ endif
 bitcoin_tx_SOURCES = bitcoin-tx.cpp
 bitcoin_tx_CPPFLAGS = $(BITCOIN_INCLUDES)
 #
+bitcoin_tx_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS)
 
 if TARGET_WINDOWS
 bitcoin_cli_SOURCES += bitcoin-cli-res.rc
 endif
+bitcoin_cli_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS)
 
 CLEANFILES = leveldb/libleveldb.a leveldb/libmemenv.a *.gcda *.gcno
 

src/Makefile.qt.include

@@ -362,7 +362,7 @@ qt_bitcoin_qt_LDADD += $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBITCOIN_UTIL)
 if USE_LIBSECP256K1
   qt_bitcoin_qt_LDADD += secp256k1/libsecp256k1.la
 endif
-qt_bitcoin_qt_LDFLAGS = $(AM_LDFLAGS) $(QT_LDFLAGS)
+qt_bitcoin_qt_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(QT_LDFLAGS)
 
 #locale/foo.ts -> locale/foo.qm
 QT_QM=$(QT_TS:.ts=.qm)

src/Makefile.qttest.include

@@ -36,7 +36,7 @@ qt_test_test_bitcoin_qt_LDADD += $(LIBBITCOIN_CLI) $(LIBBITCOIN_COMMON) $(LIBBIT
 if USE_LIBSECP256K1
   qt_test_test_bitcoin_qt_LDADD += secp256k1/libsecp256k1.la
 endif
-qt_test_test_bitcoin_qt_LDFLAGS = $(AM_LDFLAGS) $(QT_LDFLAGS)
+qt_test_test_bitcoin_qt_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(QT_LDFLAGS)
 
 CLEAN_BITCOIN_QT_TEST = $(TEST_QT_MOC_CPP) qt/test/*.gcda qt/test/*.gcno
 

src/Makefile.test.include

@@ -75,6 +75,7 @@ if USE_LIBSECP256K1
 endif
 
 test_test_bitcoin_LDADD += $(BDB_LIBS) $(SSL_LIBS) $(CRYPTO_LIBS)
+test_test_bitcoin_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS)
 
 nodist_test_test_bitcoin_SOURCES = $(GENERATED_TEST_FILES)