Make libobjc compile on i686.

Lua tests don't pass though.

cmake/libobjc.cmake

@@ -10,7 +10,7 @@ macro(libobjc_build)
             set (extra_cflags "${extra_cflags} -fno-inline")
         endif()
         set (extra_ldflags "")
-    else ()
+    else()
         set (extra_cflags "-O3")
         if (CC_HAS_WNO_UNUSED_RESULT)
             set (extra_cflags "${extra_cflags} -Wno-unused-result")
@@ -20,8 +20,11 @@ macro(libobjc_build)
         endif()
         set (extra_ldflags "-s")
     endif()
-    if (${TARGET_OS_LINUX})
+    if (TARGET_OS_LINUX)
         set (extra_cflags "${extra_cflags} -D_GNU_SOURCE")
+       if (${CMAKE_SYSTEM_PROCESSOR} MATCHES "686")
+            set (extra_cflags "${extra_cflags} -march=i586")
+       endif()
     endif()
     if (CMAKE_COMPILER_IS_CLANG)
         set (extra_cflags "${extra_cflags} -Wno-deprecated-objc-isa-usage")