```
./build.sh --debug
...
[  4%] Building C object pal/src/CMakeFiles/Chakra.Pal.dir/safecrt/safecrt_output_s.c.o
In file included from /home/ChakraCore/pal/src/safecrt/safecrt_output_s.c:45:
/home/ChakraCore/pal/src/safecrt/output.inl:854:28: error: call to undeclared function 'va_arg'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
  854 |                 fldwidth = get_int_arg(&argptr);
      |                            ^
/home/ChakraCore/pal/src/safecrt/output.inl:555:41: note: expanded from macro 'get_int_arg'
  555 |     #define get_int_arg(list)           va_arg(*list, int)
      |                                         ^
/home/ChakraCore/pal/src/safecrt/output.inl:854:28: error: expected expression
/home/ChakraCore/pal/src/safecrt/output.inl:555:55: note: expanded from macro 'get_int_arg'
  555 |     #define get_int_arg(list)           va_arg(*list, int)
...
```
It appears that `__GNUC_VA_LIST` is defined when it probably shouldn't be.
Build failure with Clang 16, 17 -- call to undeclared function 'va_arg'
This is a GitHub Issue
repo:ChakraCore
owner:chakra-core
Title : Build failure with Clang 16, 17 -- call to undeclared function 'va_arg'
Issue date:

--- start body ---
```
./build.sh --debug
...
[  4%] Building C object pal/src/CMakeFiles/Chakra.Pal.dir/safecrt/safecrt_output_s.c.o
In file included from /home/ChakraCore/pal/src/safecrt/safecrt_output_s.c:45:
/home/ChakraCore/pal/src/safecrt/output.inl:854:28: error: call to undeclared function 'va_arg'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
  854 |                 fldwidth = get_int_arg(&argptr);
      |                            ^
/home/ChakraCore/pal/src/safecrt/output.inl:555:41: note: expanded from macro 'get_int_arg'
  555 |     #define get_int_arg(list)           va_arg(*list, int)
      |                                         ^
/home/ChakraCore/pal/src/safecrt/output.inl:854:28: error: expected expression
/home/ChakraCore/pal/src/safecrt/output.inl:555:55: note: expanded from macro 'get_int_arg'
  555 |     #define get_int_arg(list)           va_arg(*list, int)
...
```
It appears that `__GNUC_VA_LIST` is defined when it probably shouldn't be.
--- end body ---
