Simple module compilation cache (#203)

* Simple module compilation cache

* Fix base64 encoding bug

* Use warn! everywhere in cache system

* Remove unused import

* Temporary workaround for long path on Windows

* Remove unused import for non-windows builds

* Add command line argument to enable cache system + apply minor review feedback

wasmtime-environ/src/lib.rs

@@ -45,11 +45,14 @@ mod module_environ;
 mod tunables;
 mod vmoffsets;
 
+mod cache;
+
 pub mod cranelift;
 #[cfg(feature = "lightbeam")]
 pub mod lightbeam;
 
 pub use crate::address_map::{FunctionAddressMap, InstructionAddressMap, ModuleAddressMap};
+pub use crate::cache::conf as cache_conf;
 pub use crate::compilation::{
     Compilation, CompileError, Compiler, Relocation, RelocationTarget, Relocations,
 };