cmake: always set -m32 for 32 bits build

It fixes cross-compilition issue when users/env set CC/CXX variables

cmake/linux-compiler-i386-multilib.cmake

@@ -4,9 +4,15 @@ set(CMAKE_SYSTEM_PROCESSOR i686)
 
 # It could be i?86-*linux-gnu, x86_64-*linux-gnu, x86_64-*linux-gnux32, etc.
 # Leave it generic to only support amd64 or x32 to i386 with any compiler.
-if("$ENV{CC}" STREQUAL "" OR "$ENV{CXX}" STREQUAL "")
+if ("$ENV{CC}" STREQUAL "")
     set(CMAKE_C_COMPILER cc -m32)
+else()
+    set(CMAKE_C_COMPILER $ENV{CC} -m32)
+endif()
+if ("$ENV{CXX}" STREQUAL "")
     set(CMAKE_CXX_COMPILER c++ -m32)
+else()
+    set(CMAKE_CXX_COMPILER $ENV{CXX} -m32)
 endif()
 
 # cmake 2.8.5 correctly sets CMAKE_LIBRARY_ARCHITECTURE for Debian multiarch.