Implement env var hack to work around potentially suboptimal cargo behaviour

Author: ProfLander

Cargo.toml

@@ -2,7 +2,6 @@
 name = "rust-gpu-builder"
 version = "0.4.0"
 edition = "2021"
-build = false
 
 [dependencies]
 rust-gpu-builder-shared = { git = "https://github.com/bevy-rust-gpu/rust-gpu-builder-shared" }

build.rs

@@ -0,0 +1,12 @@
+use std::{env, error::Error};
+
+fn main() -> Result<(), Box<dyn Error>> {
+    println!("cargo:rerun-if-changed=build.rs");
+    println!("cargo:rerun-if-env-changed=CARGO_CFG_TARGET_OS");
+    println!("cargo:rerun-if-env-changed=CARGO_CFG_TARGET_ARCH");
+    // While OUT_DIR is set for both build.rs and compiling the crate, PROFILE is only set in
+    // build.rs. So, export it to crate compilation as well.
+    let profile = env::var("PROFILE").unwrap();
+    println!("cargo:rustc-env=PROFILE={profile}");
+    Ok(())
+}

src/main.rs

@@ -104,6 +104,11 @@ impl ShaderBuilder {
 
     /// Builds a shader with the provided set of options.
     pub fn build_shader(&self) -> Result<CompileResult, SpirvBuilderError> {
+        // As per `spirv-builder`, apply env vars set in build.rs
+        // to work around potentially suboptimal cargo behaviour
+        std::env::set_var("OUT_DIR", env!("OUT_DIR"));
+        std::env::set_var("PROFILE", env!("PROFILE"));
+
         let mut builder = SpirvBuilder::new(&self.path_to_crate, &self.target)
             .deny_warnings(self.deny_warnings)
             .release(self.release)