- Apply global warnings in warnings.cmake instead of maintaining them in
separate files.
- Enable errors during CI when building iwasm and wamrc.
- Since GCC and Clang are the default compilers on Ubuntu and macOS, enabling
`-Werror` on both platforms can be treated as checking with different
compilers.
3.14 is used and tested by linux mini-product
to fix
```
CMake Error at CMakeLists.txt:4 (cmake_minimum_required):
Compatibility with CMake < 3.5 has been removed from CMake.
Update the VERSION argument <min> value. Or, use the <min>...<max> syntax
to tell CMake that the project requires at least <min> but has been updated
to work with policies introduced by <max> or earlier.
Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway.
```
Real world native libs likely need to access the wasm_runtime_xxx API.
This example demonstrates it.
Build vmlib as a shared lib to make it straightforward to share a
single runtime instance between iwasm and native libs.
When WAMR_BUILD_TARGET isn't set, choosing right target is decided
by checking `CMAKE_SIZEOF_VOID_P` variable. However, choosing `X86_32`
target is not doing specifically checking size of void pointer. It is kind
a fallback target for others.
This patch explicitly checks the size of void pointer before setting the target
to `X86_32` to fix the issue.
