Fix several issues found (#1996)

- CMakeLists.txt: add lib_export.h to install list
- Fast JIT: enlarge spill cache size to enable several standalone cases
                when hw bound check is disabled
- Thread manager: wasm_cluster_exit_thread may destroy an invalid
               exec_env->module_inst when exec_env was destroyed before
- samples/socket-api: fix failure to run timeout_client.wasm
- enhance CI build wasi-libc and sample/wasm-c-api-imports CMakeLlist.txt

.github/workflows/compilation_on_android_ubuntu.yml

@@ -367,7 +367,7 @@ jobs:
           git fetch https://github.com/WebAssembly/wasi-libc \
             8f5275796a82f8ecfd0833a4f3f444fa37ed4546
           git checkout FETCH_HEAD
-          make \
+          make -j \
             AR=/opt/wasi-sdk/bin/llvm-ar \
             NM=/opt/wasi-sdk/bin/llvm-nm \
             CC=/opt/wasi-sdk/bin/clang \