support rust-analyzer for board_qemu features

.gitignore

@@ -1,3 +1,6 @@
+.*/*
+!.github/*
+!.vscode/settings.json
 .idea
 Cargo.lock
 target

.vscode/settings.json

@@ -0,0 +1,13 @@
+{
+    // Prevent "can't find crate for `test`" error on no_std
+    // Ref: https://github.com/rust-lang/vscode-rust/issues/729
+    // For vscode-rust plugin users:
+    "rust.target": "riscv64gc-unknown-none-elf",
+    "rust.all_targets": false,
+    // For Rust Analyzer plugin users:
+    "rust-analyzer.cargo.target": "riscv64gc-unknown-none-elf",
+    "rust-analyzer.checkOnSave.allTargets": false,
+    "rust-analyzer.cargo.features": [
+        "board_qemu"
+    ]
+}

user/Cargo.toml

@@ -10,3 +10,7 @@ edition = "2018"
 
 [profile.release]
 debug = true
+
+[features]
+board_qemu = []
+board_k210 = []