libssh: Don't use the visibility flag on OS/2.

ConfigureChecks.cmake

@@ -33,12 +33,12 @@ function(COMPILER_DUMPVERSION _OUTPUT_VERSION)
     set(${_OUTPUT_VERSION} ${_COMPILER_VERSION} PARENT_SCOPE)
 endfunction()
 
-if(CMAKE_COMPILER_IS_GNUCC AND NOT MINGW)
+if(CMAKE_COMPILER_IS_GNUCC AND NOT MINGW AND NOT OS2)
     compiler_dumpversion(GNUCC_VERSION)
     if (NOT GNUCC_VERSION EQUAL 34)
         check_c_compiler_flag("-fvisibility=hidden" WITH_VISIBILITY_HIDDEN)
     endif (NOT GNUCC_VERSION EQUAL 34)
-endif(CMAKE_COMPILER_IS_GNUCC AND NOT MINGW)
+endif(CMAKE_COMPILER_IS_GNUCC AND NOT MINGW AND NOT OS2)
 
 # HEADER FILES
 check_include_file(argp.h HAVE_ARGP_H)

include/libssh/libssh.h

@@ -41,7 +41,7 @@
     #endif
   #endif
 #else
-  #if __GNUC__ >= 4
+  #if __GNUC__ >= 4 && !defined(__OS2__)
     #define LIBSSH_API __attribute__((visibility("default")))
   #else
     #define LIBSSH_API