lli should not put .bc in argv[0]

When you run a program foo linked with gccld (i.e., by running the script
"foo" it outputs which runs lli) it passes foo.bc instead of foo as the
argv[0] for the program. This is surprising to the user, who is expecting
that a program started by running "./foo" will call itself "./foo", not
"./foo.bc".

Fixed by removing ".bc" from the end of InputFile if it is there, in
tools/lli/lli.cpp:main().

Ok to commit?