Build C API release artifacts with unwind tables (#11383)

In #11344 it was found that if Wasmtime had a frame on the stack then an
application's previous unwinding was broken. This was due to the fact
that Wasmtime's C API artifacts do not have unwind information built-in
due to being build with `-Cpanic=abort`. This change updates to building
the C API artifacts with `-Cforce-unwind-tables` even though Rust itself
won't use them to assist with embedders that want to unwind. These
should in theory be easily strippable if desired and additionally
embedders always have the option to build their own version of the C API
too.

Closes #11344

Author: alexcrichton

ci/build-release-artifacts.sh

@@ -71,6 +71,12 @@ fi
 
 cargo build --release $flags --target $target -p wasmtime-cli $bin_flags --features run
 
+# For the C API force unwind tables to be emitted to make the generated objects
+# more flexible. Embedders can always build without this but this enables
+# libunwind to produce better backtraces by default when Wasmtime is linked into
+# a different project that wants to unwind.
+export RUSTFLAGS="$RUSTFLAGS -C force-unwind-tables"
+
 mkdir -p target/c-api-build
 cd target/c-api-build
 cmake \