Build for only one target for docs.rs (#5427)

* Add docs.rs metadata to all cargo.toml files

* Remove docs.rs metada in substrate's cargo.toml

substrate/test-utils/Cargo.toml

@@ -6,3 +6,6 @@ edition = "2018"
 license = "GPL-3.0"
 homepage = "https://substrate.dev"
 repository = "https://github.com/paritytech/substrate/"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]

substrate/test-utils/client/Cargo.toml

@@ -22,3 +22,6 @@ sp-core = { version = "2.0.0-alpha.5", path = "../../primitives/core" }
 sp-runtime = { version = "2.0.0-alpha.5", path = "../../primitives/runtime" }
 sp-blockchain = { version = "2.0.0-alpha.5", path = "../../primitives/blockchain" }
 sp-state-machine = { version = "0.8.0-alpha.5", path = "../../primitives/state-machine" }
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]

substrate/test-utils/runtime/Cargo.toml

@@ -87,3 +87,6 @@ std = [
 	"sp-transaction-pool/std",
 	"trie-db/std",
 ]
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]

substrate/test-utils/runtime/client/Cargo.toml

@@ -20,3 +20,6 @@ codec = { package = "parity-scale-codec", version = "1.3.0" }
 sc-client-api = { version = "2.0.0-alpha.5", path = "../../../client/api" }
 sc-client = { version = "0.8.0-alpha.5", path = "../../../client/" }
 futures = "0.3.4"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]

substrate/test-utils/runtime/transaction-pool/Cargo.toml

@@ -18,3 +18,6 @@ sp-transaction-pool = { version = "2.0.0-alpha.5", path = "../../../primitives/t
 sc-transaction-graph = { version = "2.0.0-alpha.5", path = "../../../client/transaction-pool/graph" }
 futures = { version = "0.3.1", features = ["compat"] }
 derive_more = "0.99.2"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]