build(win): make the mingw cross-compile link and find librustzcash

Three things broke the x86_64-w64-mingw32 build; two are real and fixed
here (the third was a stale-object contamination from building Linux and
Windows in the same tree, resolved by a clean rebuild — not a code fix).

1. Single-pass mingw ld could not resolve the cross-references DragonX
   added between the internal static archives (libbitcoin_util/common
   objects pulling in UniValue; util<->common mutual deps). GNU ld on
   Linux re-scans archives so it never surfaced; ld64 on macOS rejects
   the grouping flag outright. Bracket each binary's _LDADD in
   -Wl,--start-group/--end-group, delivered via AC_SUBST(LINK_GROUP_*)
   so automake does not reject the linker flag inside _LDADD, and left
   empty on every non-Windows target.

2. The Rust build emits the mingw archive as rustzcash.lib, but the
   link line asks for -lrustzcash, i.e. librustzcash.a. Normalize the
   staged filename to librustzcash.a for every host (a no-op on
   Linux/macOS, where the basename was already librustzcash.a).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

configure.ac

@@ -833,6 +833,22 @@ AM_CONDITIONAL([TARGET_DARWIN], [test x$TARGET_OS = xdarwin])
 AM_CONDITIONAL([BUILD_DARWIN], [test x$BUILD_OS = xdarwin])
 AM_CONDITIONAL([TARGET_LINUX], [test x$TARGET_OS = xlinux])
 AM_CONDITIONAL([TARGET_WINDOWS], [test x$TARGET_OS = xwindows])
+
+dnl mingw ld is single-pass: bracket the internal static archives in a link group
+dnl so it re-scans and resolves the cross-references DragonX added between them
+dnl (libbitcoin_util/common objects using UniValue; util<->common mutual deps).
+dnl Delivered via AC_SUBST (not an automake conditional) so automake does not
+dnl reject the linker flags inside _LDADD. Empty elsewhere (macOS ld64 rejects the
+dnl flag; GNU ld on Linux re-scans archives already).
+if test "x$TARGET_OS" = "xwindows"; then
+  LINK_GROUP_START="-Wl,--start-group"
+  LINK_GROUP_END="-Wl,--end-group"
+else
+  LINK_GROUP_START=""
+  LINK_GROUP_END=""
+fi
+AC_SUBST(LINK_GROUP_START)
+AC_SUBST(LINK_GROUP_END)
 AM_CONDITIONAL([ENABLE_WALLET],[test x$enable_wallet = xyes])
 AM_CONDITIONAL([ENABLE_MINING],[test x$enable_mining = xyes])
 AM_CONDITIONAL([ENABLE_TESTS],[test x$BUILD_TEST = xyes])

depends/packages/librustzcash.mk

@@ -53,6 +53,6 @@ endif
 define $(package)_stage_cmds
   mkdir $($(package)_staging_dir)$(host_prefix)/lib/ && \
   mkdir $($(package)_staging_dir)$(host_prefix)/include/ && \
-  cp $($(package)_library_file) $($(package)_staging_dir)$(host_prefix)/lib/ && \
+  cp $($(package)_library_file) $($(package)_staging_dir)$(host_prefix)/lib/librustzcash.a && \
   cp librustzcash/include/librustzcash.h $($(package)_staging_dir)$(host_prefix)/include/
 endef

src/Makefile.am

@@ -489,7 +489,7 @@ if TARGET_WINDOWS
 dragonxd_SOURCES += bitcoind-res.rc
 endif
 
-dragonxd_LDADD = \
+dragonxd_LDADD = $(LINK_GROUP_START) \
   $(LIBBITCOIN_SERVER) \
   $(LIBCURL) \
   $(LIBBITCOIN_COMMON) \
@@ -527,6 +527,8 @@ if TARGET_LINUX
 dragonxd_LDADD += libcc.so $(LIBSECP256K1)
 endif
 
+dragonxd_LDADD += $(LINK_GROUP_END)
+
 # [+] Decker: use static linking for libstdc++.6.dylib, libgomp.1.dylib, libgcc_s.1.dylib
 if TARGET_DARWIN
 dragonxd_LDFLAGS += -static-libgcc
@@ -553,7 +555,7 @@ if TARGET_WINDOWS
 dragonx_cli_SOURCES += bitcoin-cli-res.rc
 endif
 
-dragonx_cli_LDADD = \
+dragonx_cli_LDADD = $(LINK_GROUP_START) \
 	$(LIBBITCOIN_CLI) \
 	$(LIBUNIVALUE) \
 	$(LIBBITCOIN_UTIL) \
@@ -566,8 +568,10 @@ dragonx_cli_LDADD = \
 	$(LIBBITCOIN_CRYPTO) \
 	$(LIBZCASH_LIBS)
 
+dragonx_cli_LDADD += $(LINK_GROUP_END)
+
 if ENABLE_WALLET
-wallet_utility_LDADD = \
+wallet_utility_LDADD = $(LINK_GROUP_START) \
 	libbitcoin_wallet.a \
 	$(LIBBITCOIN_COMMON) \
 	$(LIBBITCOIN_CRYPTO) \
@@ -579,6 +583,7 @@ wallet_utility_LDADD = \
 	$(LIBZCASH) \
 	$(LIBZCASH_LIBS)\
     $(LIBRANDOMX)
+wallet_utility_LDADD += $(LINK_GROUP_END)
 endif
 
 # hush-tx binary #
@@ -591,7 +596,7 @@ if TARGET_WINDOWS
 dragonx_tx_SOURCES += bitcoin-tx-res.rc
 endif
 
-dragonx_tx_LDADD = \
+dragonx_tx_LDADD = $(LINK_GROUP_START) \
   $(LIBUNIVALUE) \
   $(LIBBITCOIN_COMMON) \
   $(LIBBITCOIN_UTIL) \
@@ -602,7 +607,7 @@ dragonx_tx_LDADD = \
   $(LIBZCASH_LIBS) \
   $(LIBRANDOMX)
 
-dragonx_tx_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS)
+dragonx_tx_LDADD += $(BOOST_LIBS) $(CRYPTO_LIBS) $(LINK_GROUP_END)
 
 # Zcash Protocol Primitives
 libzcash_a_SOURCES = \