[ELF] - Add test case to test 32 bits output.

We had no tests that checked how we print -Map output for
32 bit targets. Though there are at least 2 places where we have the difference.
(between 64 and 32 bits):

https://github.com/llvm-mirror/lld/blob/master/ELF/MapFile.cpp#L52
https://github.com/llvm-mirror/lld/blob/master/ELF/MapFile.cpp#L162

Patch adds just a trivial test to check we do right things in general.

llvm-svn: 335954