Move generated exported lib.rs into src/ subdir

Signed-off-by: Matt Leon <mattleon@google.com>

Author: leonm1

bazel/external/wasmtime.BUILD

@@ -32,7 +32,7 @@ cc_library(
 rust_static_library(
     name = "wasmtime_lib_staticlib",
     srcs = [
-        "lib.rs",
+        "src/lib.rs",
     ],
     edition = "2021",
     deps = [

bazel/repositories.bzl

@@ -396,7 +396,7 @@ def proxy_wasm_cpp_host_repositories():
              -e 's/\\[wasm_/\\[wasmtime_wasm_/g'                 \
              -e 's/wasmtime_config_wasm_/wasmtime_config_wasmtime_wasm_/g' \
              -e 's/(wasm_/(wasmtime_wasm_/g' {} \\;
-          cat >lib.rs <<EOF
+          cat >src/lib.rs <<EOF
 pub use wasmtime_c_api;
 EOF
         """],