LLVM Discussion Forums

How to generate .ll and .bc for arm

how to generate .ll file and .bc file for arm v7a on x86

.ll and .bc both are mostly target-independent. but You can use clang -S --target=yourtarget to emit target assembly in .s format.
See this thread LLVM build.
Also, See Getting started example with clang to understand the pipeline.
And Cross compiling using clang.

I think you should read some background of LLVM first:-
LLVM chapter from AOSA book
Introducing LLVM Intermediate Representation from Getting Started with LLVM Core Libraries