Check cranelift when using the cargo-clif executable (#1047)

* Check cranelift when using the cargo-clif executable

* Check for both

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Co-authored-by: Justin Smith <justsmth@amazon.com>

Author: frederikhors

aws-lc-sys/builder/main.rs

@@ -271,7 +271,7 @@ fn is_cranelift_backend() -> bool {
     // CARGO_ENCODED_RUSTFLAGS contains flags separated by 0x1f (ASCII Unit Separator)
     if let Some(rustflags) = optional_env("CARGO_ENCODED_RUSTFLAGS") {
         for flag in rustflags.split('\x1f') {
-            if flag.contains("codegen-backend=cranelift") {
+            if flag.contains("codegen-backend") && flag.contains("cranelift") {
                 return true;
             }
         }