Cygwin: dumper: also link with libzstd, as libbfd may require it

Also allow that linkage to be dynamic, as libzstd-devel doesn't
currently provide a static library.

.appveyor.yml

@@ -35,6 +35,7 @@ patch,\
 cocom,\
 gettext-devel,\
 libiconv-devel,\
+libzstd-devel,\
 zlib-devel,\
 %PKGARCH%-gcc-core,\
 %PKGARCH%-gcc-g++,\

.github/workflows/cygwin.yml

@@ -80,6 +80,7 @@ jobs:
           gettext-devel,
           libiconv,
           libiconv-devel,
+          libzstd-devel,
           make,
           mingw64-${{ matrix.pkgarch }}-gcc-g++,
           mingw64-${{ matrix.pkgarch }}-zlib,

winsup/configure.ac

@@ -116,6 +116,13 @@ AC_CHECK_LIB([bfd], [bfd_init], [true],
 
 AM_CONDITIONAL(BUILD_DUMPER, [test "x$ac_cv_lib_bfd_bfd_init" = "xyes"])
 
+# libbfd.a doesn't have a pkgconfig file, so we guess what it's dependencies
+# are, based on what's present in the build environment
+BFD_LIBS="-lintl -liconv -liberty -lz"
+AC_CHECK_LIB([sframe], [sframe_decode], [BFD_LIBS="${BFD_LIBS} -lsframe"])
+AC_CHECK_LIB([zstd], [ZSTD_isError], [BFD_LIBS="${BFD_LIBS} -lzstd"])
+AC_SUBST([BFD_LIBS])
+
 AC_CONFIG_FILES([
     Makefile
     cygwin/Makefile

winsup/doc/faq-programming.xml

@@ -679,7 +679,7 @@ rewriting the runtime library in question from specs...
 installed; you at least need <literal>gcc-g++</literal>,
 <literal>make</literal>, <literal>automake</literal>,
 <literal>autoconf</literal>, <literal>git</literal>, <literal>perl</literal>,
-<literal>gettext-devel</literal>, <literal>libiconv-devel</literal>
+<literal>gettext-devel</literal>, <literal>libiconv-devel</literal>, <literal>libzstd-devel</literal>,
 <literal>zlib-devel</literal>, <literal>cocom</literal> and <literal>patch</literal>.
 </para>
 

winsup/utils/Makefile.am

@@ -78,7 +78,8 @@ LDADD = -lnetapi32
 cygpath_CXXFLAGS = -fno-threadsafe-statics $(AM_CXXFLAGS)
 cygpath_LDADD = $(LDADD) -luserenv -lntdll
 dumper_CXXFLAGS = -I$(top_srcdir)/../include $(AM_CXXFLAGS)
-dumper_LDADD = $(LDADD) -lpsapi -lbfd -lintl -liconv -liberty -lz -lntdll
+dumper_LDADD = $(LDADD) -lpsapi -lntdll -lbfd @BFD_LIBS@
+dumper_LDFLAGS =
 ldd_LDADD = $(LDADD) -lpsapi -lntdll
 mount_CXXFLAGS = -DFSTAB_ONLY $(AM_CXXFLAGS)
 minidumper_LDADD = $(LDADD) -ldbghelp