Use rust_shared_library for building Wasm modules. (#512)

The rust_binary(out_binary=True) hack is no longer needed,
and we can remove the patch for it.

Signed-off-by: Piotr Sikora <code@piotrsikora.dev>
Signed-off-by: Matt Leon <mattleon@google.com>

Author: PiotrSikora

bazel/external/rules_rust.patch

@@ -139,8 +139,6 @@ def proxy_wasm_cpp_host_repositories():
         name = "rules_rust",
         integrity = "sha256-u8dkwlLQYSgbI1knek1GSA4tz69yr8HObgCtpYzL/Uw=",
         urls = ["https://github.com/bazelbuild/rules_rust/releases/download/0.69.0/rules_rust-0.69.0.tar.gz"],
-        patches = ["@proxy_wasm_cpp_host//bazel/external:rules_rust.patch"],
-        patch_args = ["-p1"],
     )
 
     # Core deps. Keep them updated.

bazel/repositories.bzl

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-load("@rules_rust//rust:defs.bzl", "rust_binary")
+load("@rules_rust//rust:defs.bzl", "rust_shared_library")
 
 def _wasm_rust_transition_impl(settings, attr):
     return {
@@ -81,11 +81,9 @@ def wasm_rust_binary(name, tags = [], wasi = False, signing_key = [], **kwargs):
     wasm_name = "_wasm_" + name.replace(".", "_")
     kwargs.setdefault("visibility", ["//visibility:public"])
 
-    rust_binary(
+    rust_shared_library(
         name = wasm_name,
         edition = "2018",
-        crate_type = "cdylib",
-        out_binary = True,
         tags = ["manual"],
         **kwargs
     )