Add feature "system-libs" to enable linking against system libraries

If this feature is enabled, libsodium-sys and zstd-sys will link
dynamically against system-provided libraries instead of building
and linking statically the bundled (possibly outdated and vulnerable)
copies of them. This feature is intended mainly for linux package
maintainers.

Cargo.lock

@@ -4140,4 +4140,5 @@ checksum = "2daf2f248d9ea44454bfcb2516534e8b8ad2fc91bf818a1885495fc42bc8ac9f"
 dependencies = [
  "cc",
  "libc",
+ "pkg-config",
 ]

src/block/Cargo.toml

@@ -36,3 +36,7 @@ serde_bytes = "0.11"
 futures = "0.3"
 futures-util = "0.3"
 tokio = { version = "1.0", default-features = false, features = ["rt", "rt-multi-thread", "io-util", "net", "time", "macros", "sync", "signal", "fs"] }
+
+
+[features]
+system-libs = [ "zstd/pkg-config" ]

src/garage/Cargo.toml

@@ -76,3 +76,4 @@ base64 = "0.13"
 [features]
 kubernetes-discovery = [ "garage_rpc/kubernetes-discovery" ]
 k2v = [ "garage_util/k2v", "garage_api/k2v" ]
+system-libs = [ "garage_block/system-libs", "garage_rpc/system-libs", "sodiumoxide/use-pkg-config" ]

src/rpc/Cargo.toml

@@ -54,3 +54,4 @@ hyper = { version = "0.14", features = ["client", "http1", "runtime", "tcp"] }
 
 [features]
 kubernetes-discovery = [ "kube", "k8s-openapi", "openssl", "schemars" ]
+system-libs = [ "sodiumoxide/use-pkg-config" ]