Use no-std-compat to build no-std.

Cargo.toml

@@ -41,7 +41,7 @@ internals = []                  # expose internal data structures
 unicode-xid-ident = ["unicode-xid"] # allow Unicode Standard Annex #31 for identifiers.
 metadata = ["serde_json", "rhai_codegen/metadata"] # enable exporting functions metadata
 
-no_std = ["num-traits/libm", "core-error", "libm", "ahash/compile-time-rng"]
+no_std = ["no-std-compat", "num-traits/libm", "core-error", "libm", "ahash/compile-time-rng"]
 
 # compiling for WASM
 wasm-bindgen = ["instant/wasm-bindgen"]
@@ -53,6 +53,12 @@ codegen-units = 1
 #opt-level = "z"     # optimize for size
 #panic = 'abort'     # remove stack backtrace for no-std
 
+[dependencies.no-std-compat]
+version = "0.4"
+default_features = false
+features = ["alloc"]
+optional = true
+
 [dependencies.libm]
 version = "0.2"
 default_features = false