[MC] Fix assembler infinite loop on EH table using LEB padding.

Fix the infinite loop reported in PR35809. It can occur with GCC-style
EH table assembly, where the compiler relies on the assembler to
calculate the offsets in the EH table.

Also see https://sourceware.org/bugzilla/show_bug.cgi?id=4029 for the
equivalent issue in the GNU assembler.

Patch by Ryan Prichard!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323934 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed