
If we attempt to use unwind_shared when LIBUNWIND_ENABLE_SHARED is OFF,
we'll get link errors. LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_SHARED_LIBRARY
avoids that, but it seems redundant to have to specify it manually.
Automatically switch libunwind statically when its shared build is
disabled, which also matches compiler-rt [1].
[1] 71bfec762b/compiler-rt/CMakeLists.txt (L238-L240)
Reviewed By: #libc_abi, phosek
Differential Revision: https://reviews.llvm.org/D158789