refactor(users/glittershark): Rename to grfn

Rename my //users directory and all places that refer to glittershark to
grfn, including nix references and documentation.

This may require some extra attention inside of gerrit's database after
it lands to allow me to actually push things.

Change-Id: I4728b7ec2c60024392c1c1fa6e0d4a59b3e266fa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2933
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: lukegb <lukegb@tvl.fyi>
Reviewed-by: glittershark <grfn@gws.fyi>

users/grfn/achilles/src/codegen/mod.rs

@@ -0,0 +1,25 @@
+pub mod llvm;
+
+use inkwell::execution_engine::JitFunction;
+use inkwell::OptimizationLevel;
+pub use llvm::*;
+
+use crate::ast::hir::Expr;
+use crate::ast::Type;
+use crate::common::Result;
+
+pub fn jit_eval<T>(expr: &Expr<Type>) -> Result<T> {
+    let context = Context::create();
+    let mut codegen = Codegen::new(&context, "eval");
+    let execution_engine = codegen
+        .module
+        .create_jit_execution_engine(OptimizationLevel::None)
+        .map_err(Error::from)?;
+    codegen.codegen_function("test", &[], &expr)?;
+
+    unsafe {
+        let fun: JitFunction<unsafe extern "C" fn() -> T> =
+            execution_engine.get_function("eval").unwrap();
+        Ok(fun.call())
+    }
+}