ENH: try and fix aix xlC with gcc

Modules/Platform/AIX.cmake

@@ -8,14 +8,14 @@ SET(CMAKE_SHARED_LIBRARY_LINK_C_FLAGS "-Wl,-brtl,-bexpall")  # +s, flag for exe
 IF(CMAKE_COMPILER_IS_GNUCXX) 
   SET(CMAKE_SHARED_LIBRARY_CREATE_CXX_FLAGS "-shared -Wl,-G")       # -shared
 ELSE(CMAKE_COMPILER_IS_GNUCXX) 
-  SET(CMAKE_SHARED_LIBRARY_CXX_FLAGS "")
-  SET(CMAKE_SHARED_MODULE_CXX_FLAGS  "")
+  SET(CMAKE_SHARED_LIBRARY_CXX_FLAGS " ")
+  SET(CMAKE_SHARED_MODULE_CXX_FLAGS  " ")
 ENDIF(CMAKE_COMPILER_IS_GNUCXX) 
 
 # C Compiler
 IF(CMAKE_COMPILER_IS_GNUCC)
   SET(CMAKE_SHARED_LIBRARY_CREATE_C_FLAGS "-shared -Wl,-G")       # -shared
 ELSE(CMAKE_COMPILER_IS_GNUCC)
-  SET(CMAKE_SHARED_LIBRARY_C_FLAGS "")
-  SET(CMAKE_SHARED_MODULE_C_FLAGS  "")
+  SET(CMAKE_SHARED_LIBRARY_C_FLAGS " ")
+  SET(CMAKE_SHARED_MODULE_C_FLAGS  " ")
 ENDIF(CMAKE_COMPILER_IS_GNUCC)