Fix compilation with visibility flags with mingw.

Thanks to Patrick Spendrin.

ConfigureChecks.cmake

@@ -16,7 +16,9 @@ set(SYSCONFDIR ${SYSCONF_INSTALL_DIR})
 set(BINARYDIR ${CMAKE_BINARY_DIR})
 set(SOURCEDIR ${CMAKE_SOURCE_DIR})
 
+if(CMAKE_COMPILER_IS_GNUC)
 check_c_compiler_flag("-fvisibility=hidden" WITH_VISIBILITY_HIDDEN)
+endif(CMAKE_COMPILER_IS_GNUC)
 
 # HEADER FILES
 check_include_file(pty.h HAVE_PTY_H)

libssh/CMakeLists.txt

@@ -73,10 +73,6 @@ if (GCRYPT_LIBRARY)
   )
 endif (GCRYPT_LIBRARY)
 
-if (WITH_VISIBILITY_HIDDEN)
-  set(LIBSSH_SHARED_CFLAGS "-fvisibility=hidden")
-endif (WITH_VISIBILITY_HIDDEN)
-
 set(libssh_SRCS
   agent.c
   auth.c
@@ -158,10 +154,13 @@ set_target_properties(
         ssh
       DEFINE_SYMBOL
         LIBSSH_EXPORTS
-      COMPILE_FLAGS
-        ${LIBSSH_SHARED_CFLAGS}
 )
 
+if (WITH_VISIBILITY_HIDDEN)
+  set_target_properties(${LIBSSH_SHARED_LIBRARY} PROPERTIES COMPILE_FLAGS "-fvisibility=hidden")
+endif (WITH_VISIBILITY_HIDDEN)
+
+
 install(
   TARGETS
     ${LIBSSH_SHARED_LIBRARY}