Default to no glam provider, add compile error re. enabling one

Author: ProfLander

Cargo.toml

@@ -4,7 +4,7 @@ version = "0.1.0"
 edition = "2021"
 
 [features]
-default = ["glam"]
+default = []
 glam = ["dep:glam"]
 spirv-std = ["dep:spirv-std"]
 

src/lib.rs

@@ -7,12 +7,15 @@
 
 #![no_std]
 
-#[cfg(not(feature = "spirv-std"))]
+#[cfg(feature = "glam")]
 pub use glam;
 
 #[cfg(feature = "spirv-std")]
 pub use spirv_std::glam;
 
+#[cfg(all(not(feature = "glam"), not(feature = "spirv-std")))]
+compile_error!("Either the glam or spirv-std feature must be enabled.");
+
 pub mod reflect;
 pub mod saturate;
 pub mod smooth_step;