Merge pull request #298 from roc-lang/fix-ci

Use `c_char` instead of `i8` for argument FFI

crates/roc_host_lib/src/lib.rs

@@ -1,12 +1,13 @@
 use roc_env::arg::ArgToAndFromHost;
+use std::ffi::c_char;
 
 /// # Safety
 /// This function is the entry point for the program, it will be linked by roc using the legacy linker
 /// to produce the final executable.
 ///
 /// Note we use argc and argv to pass arguments to the program instead of std::env::args().
 #[no_mangle]
-pub unsafe extern "C" fn main(argc: usize, argv: *const *const i8) -> i32 {
+pub unsafe extern "C" fn main(argc: usize, argv: *const *const c_char) -> i32 {
     let args = std::slice::from_raw_parts(argv, argc)
         .iter()
         .map(|&c_ptr| {