Adds BORING_ADDITIONAL_INCLUDE_PATH env variable handling

Author: Isaiah Becker-Mayer

boring-sys/build/config.rs

@@ -24,6 +24,7 @@ pub(crate) struct Features {
 pub(crate) struct Env {
     pub(crate) path: Option<PathBuf>,
     pub(crate) include_path: Option<PathBuf>,
+    pub(crate) additional_include_path: Option<PathBuf>,
     pub(crate) source_path: Option<PathBuf>,
     pub(crate) precompiled_bcm_o: Option<PathBuf>,
     pub(crate) assume_patched: bool,
@@ -146,6 +147,8 @@ impl Env {
         Self {
             path: boringssl_var("BORING_BSSL_PATH").map(PathBuf::from),
             include_path: boringssl_var("BORING_BSSL_INCLUDE_PATH").map(PathBuf::from),
+            additional_include_path: boringssl_var("BORING_ADDITIONAL_INCLUDE_PATH")
+                .map(PathBuf::from),
             source_path: boringssl_var("BORING_BSSL_SOURCE_PATH").map(PathBuf::from),
             precompiled_bcm_o: boringssl_var("BORING_BSSL_PRECOMPILED_BCM_O").map(PathBuf::from),
             assume_patched: boringssl_var("BORING_BSSL_ASSUME_PATCHED")

boring-sys/build/main.rs

@@ -690,6 +690,12 @@ fn main() {
         .clang_arg("-I")
         .clang_arg(include_path.display().to_string());
 
+    if let Some(additional_include_path) = config.env.additional_include_path {
+        builder = builder
+            .clang_arg("-I")
+            .clang_arg(additional_include_path.display().to_string());
+    }
+
     if let Some(sysroot) = &config.env.sysroot {
         builder = builder
             .clang_arg("--sysroot")