Assorted fixes for Windows compilation (#778)

* Use OS convention when splitting AWS_LC_SYS*_INCLUDES

Fixes #777

* Account for bindgen's configuration envvars

Fixes #776

Author: amyspark

aws-lc-fips-sys/builder/main.rs

@@ -107,7 +107,7 @@ pub(crate) fn get_generated_include_path(manifest_dir: &Path) -> PathBuf {
 
 pub(crate) fn get_aws_lc_fips_sys_includes_path() -> Option<Vec<PathBuf>> {
     option_env("AWS_LC_FIPS_SYS_INCLUDES")
-        .map(|colon_delim_paths| colon_delim_paths.split(':').map(PathBuf::from).collect())
+        .map(|v| std::env::split_paths(&v).collect())
 }
 
 #[allow(dead_code)]

aws-lc-fips-sys/builder/sys_bindgen.rs

@@ -56,7 +56,8 @@ fn prepare_bindings_builder(manifest_dir: &Path, options: &BindingOptions) -> bi
                 .join("rust_wrapper.h")
                 .display()
                 .to_string(),
-        );
+        )
+        .parse_callbacks(Box::new(bindgen::CargoCallbacks::new()));
 
     if !options.disable_prelude {
         builder = builder.raw_line(PRELUDE);

aws-lc-sys/builder/main.rs

@@ -118,7 +118,7 @@ pub(crate) fn get_generated_include_path(manifest_dir: &Path) -> PathBuf {
 
 pub(crate) fn get_aws_lc_sys_includes_path() -> Option<Vec<PathBuf>> {
     option_env("AWS_LC_SYS_INCLUDES")
-        .map(|colon_delim_paths| colon_delim_paths.split(':').map(PathBuf::from).collect())
+      .map(|v| std::env::split_paths(&v).collect())
 }
 
 #[allow(dead_code)]