Use docker to build static releases

Static builds are possible with the musl C library.
glibc is capricious when it comes to static linking and DNS support (and
other things).

Dockerfile

@@ -0,0 +1,27 @@
+FROM alpine:3.10
+
+WORKDIR /build
+
+RUN apk add --no-cache wget cmake make gcc g++ linux-headers zlib-dev openssl-dev \
+            automake autoconf libevent-dev ncurses-dev msgpack-c-dev libexecinfo-dev \
+            ncurses-static libexecinfo-static libevent-static msgpack-c ncurses-libs \
+            libevent libexecinfo openssl zlib
+
+RUN set -ex; \
+	mkdir -p /src/libssh/build; \
+	cd /src; \
+	wget -O libssh.tar.xz https://www.libssh.org/files/0.9/libssh-0.9.0.tar.xz; \
+	tar -xf libssh.tar.xz -C /src/libssh --strip-components=1; \
+	cd /src/libssh/build; \
+	cmake -DCMAKE_INSTALL_PREFIX:PATH=/usr \
+                -DWITH_SFTP=OFF -DWITH_SERVER=OFF -DWITH_PCAP=OFF \
+                -DWITH_STATIC_LIB=ON -DWITH_GSSAPI=OFF ..; \
+	make -j $(nproc); \
+	make install
+
+COPY . .
+
+RUN ./autogen.sh
+RUN ./configure --enable-static
+RUN make -j $(nproc)
+RUN strip tmate

configure.ac

@@ -47,10 +47,11 @@ AC_ARG_ENABLE(
 	found_static=$enable_static
 )
 if test "x$found_static" = xyes; then
+        # XXX Static build are only doable with the musl library
 	PKG_CONFIG="pkg-config --static"
 
 	CFLAGS="$CFLAGS -flto"
-	LDFLAGS="$LDFLAGS -flto"
+	LDFLAGS="$LDFLAGS -flto -static -no-pie"
 
 	PKG_CHECK_MODULES([ZLIB], [zlib], [
 		CPPFLAGS="$ZLIB_CFLAGS $CPPFLAGS"
@@ -61,7 +62,6 @@ if test "x$found_static" = xyes; then
 		CPPFLAGS="$LIBCRYPTO_CFLAGS $CPPFLAGS"
 		LIBS="$LIBCRYPTO_LIBS $LIBS"
 	])
-  # See more static settings below... (search for found_static)
 fi
 
 # Is this gcc?
@@ -462,17 +462,6 @@ if test "x$found_getopt" != xno; then
 fi
 AM_CONDITIONAL(NO_GETOPT, [test "x$found_getopt" = xno])
 
-if test "x$found_static" = xyes; then
-	# libc and libdl should be dynamically linked.
-	# but we want to lower our requirements for libc's version.
-	# so we extract some symobls and add them here
-	if test `uname -m` = x86_64; then
-		LIBS="compat/memcpy.o -Wl,--wrap=memcpy $LIBS"
-	fi
-	LIBS="compat/clock_gettime.o libc/fdelt_chk.o $LIBS"
-	LIBS="-Wl,-Bstatic ${LIBS/-ldl/} -Wl,-Bdynamic -ldl"
-fi
-
 # Check for BSD-style integer types.
 AC_MSG_CHECKING(for BSD-style unsigned types)
 AC_COMPILE_IFELSE([AC_LANG_SOURCE(