Force pthread linkage until there's a better idea, proxy jump support
uses pthread functions whether or not pthread was linked.
(https://gitlab.com/libssh/libssh-mirror/-/issues/286)

Index: src/CMakeLists.txt
--- src/CMakeLists.txt.orig
+++ src/CMakeLists.txt
@@ -56,6 +56,13 @@ if (MINGW AND Threads_FOUND)
   )
 endif()
 
+if (Threads_FOUND)
+  set(LIBSSH_LINK_LIBRARIES
+    ${LIBSSH_LINK_LIBRARIES}
+    pthread
+  )
+endif()
+
 # The ws2_32 needs to be last for mingw to build
 # https://gitlab.com/libssh/libssh-mirror/-/issues/84
 if (WIN32)
