libs: Move cstr!() into its own crate
Make the macro host_supported, for unittests.
This overshadows the homonymous crate from crates.io [1] but importing
and depending on an external crate for <10 lines of code seems overkill.
[1]: https://crates.io/crates/cstr
Bug: 308694211
Test: atest libcstr.tests
Test: m libcstr
Test: m pvmfw_bin rialto_bin vmbase_example_bin
Change-Id: If1bf37034fc004a380b3ba528b9d76393a865d3e
diff --git a/pvmfw/src/crypto.rs b/pvmfw/src/crypto.rs
index 2b3d921..8f31553 100644
--- a/pvmfw/src/crypto.rs
+++ b/pvmfw/src/crypto.rs
@@ -33,7 +33,7 @@
use bssl_ffi::EVP_aead_aes_256_gcm_randnonce;
use bssl_ffi::EVP_AEAD;
use bssl_ffi::EVP_AEAD_CTX;
-use vmbase::cstr;
+use cstr::cstr;
#[derive(Debug)]
pub struct Error {