Disable shrink-wrap for Thumb1

Summary: In ARMConstantIslandPass, which runs after Shrink Wrap pass, long jumps will be fixed up as BL (tBfar) which depends on spilling LR in epilogue.  However, shrink-wrap may remove the LR, which causes issues when the function returns.

Reviewers: qcolombet, rengolin

Subscribers: aemerson, rengolin

Differential Revision: http://reviews.llvm.org/D15984

llvm-svn: 257187