CheckIPOSupported test code is not warning-free
https://cmake.org/cmake/help/latest/policy/CMP0138.html made CheckIPOSupported use flags from the project.
while it's a good improvement, the check now can fail if the project is using tighter compiler options.
eg.
/Users/yamamoto/git/toywasm/b/CMakeFiles/_CMakeLTOTest-C/src/main.c:1:8: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
1 | int foo();
| ^
| void
1 error generated.
ninja: build stopped: subcommand failed.