Apply clang-format for core/iwasm compilation and libraries (#784)

Apply clang-format for core/iwasm/compilation and core/iwasm/libraries files.
Add wasm-c-api empty_imports sample to workflow test.
And enable triggering workflow when core/config.h changes.

.github/workflows/compilation_on_android_ubuntu_macos.yml

@@ -399,6 +399,7 @@ jobs:
           cmake --build . --config Release --parallel 4
           ./callback
           ./callback_chain
+          ./empty_imports
           ./global
           ./hello
           ./hostref

.github/workflows/spec_test.yml

@@ -6,6 +6,7 @@ on:
   # will be triggered on PR events
   pull_request:
     paths:
+      - "core/config.h"
       - "core/iwasm/**"
       - "core/shared/**"
       - "wamr-compiler/**"
@@ -13,6 +14,7 @@ on:
   # will be triggered on push events
   push:
     paths:
+      - "core/config.h"
       - "core/iwasm/**"
       - "core/shared/**"
       - "wamr-compiler/**"