build: bump libc from 0.2.120 to 0.2.121 in /fuzz

Bumps [libc](https://github.com/rust-lang/libc) from 0.2.120 to 0.2.121.
- [Release notes](https://github.com/rust-lang/libc/releases)
- [Commits](https://github.com/rust-lang/libc/compare/0.2.120...0.2.121)

---
updated-dependencies:
- dependency-name: libc
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

fuzz/Cargo.lock

@@ -377,9 +377,9 @@ checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
 [[package]]
 name = "libc"
-version = "0.2.120"
+version = "0.2.121"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ad5c14e80759d0939d013e6ca49930e59fc53dd8e5009132f76240c179380c09"
+checksum = "efaa7b300f3b5fe8eb6bf21ce3895e1751d9665086af2d64b42f19701015ff4f"
 
 [[package]]
 name = "libfuzzer-sys"
@@ -849,6 +849,7 @@ dependencies = [
  "serde",
  "serde_derive",
  "serde_json",
+ "thiserror",
  "versionize",
  "versionize_derive",
  "vhost",

fuzz/Cargo.toml

@@ -10,7 +10,7 @@ cargo-fuzz = true
 
 [dependencies]
 block_util = { path = "../block_util" }
-libc = "0.2.120"
+libc = "0.2.121"
 libfuzzer-sys = "0.4.3"
 qcow = { path = "../qcow" }
 seccompiler = "0.2.0"