Read ldflags from info file.

bc2native script will read *.info generated from le32-none-ndk-link.
And generate the ldflags from it.

Also fix ARMEH test fails:

1. Add default flags for llc arm:

-arm-enable-ehabi
-arm-enable-ehabi-descriptors

2. For ARM, generate assembly first and
   call the assembler to produce relocatables.

Cherry picked from release_32 branch.
Patch by Lai Wei-Chih <Robert.Lai@mediatek.com>

Changes from original patch:

1. -arm-ignore-has-ras is no longer needed.