Make rust-analyzer run flycheck on the build system

.vscode/settings.json

@@ -4,7 +4,7 @@
     "rust-analyzer.imports.granularity.enforce": true,
     "rust-analyzer.imports.granularity.group": "module",
     "rust-analyzer.imports.prefix": "crate",
-    "rust-analyzer.cargo.features": ["unstable-features"],
+    "rust-analyzer.cargo.features": ["unstable-features", "__check_build_system_using_ra"],
     "rust-analyzer.linkedProjects": [
         "./Cargo.toml",
         {
@@ -32,12 +32,6 @@
         {
             "sysroot_src": "./build_sysroot/sysroot_src/library",
             "crates": [
-                {
-                    "root_module": "./y.rs",
-                    "edition": "2021",
-                    "deps": [],
-                    "cfg": [],
-                },
                 {
                     "root_module": "./example/std_example.rs",
                     "edition": "2015",

Cargo.toml

@@ -3,6 +3,13 @@ name = "rustc_codegen_cranelift"
 version = "0.1.0"
 edition = "2021"
 
+[[bin]]
+# This is used just to teach rust-analyzer how to check the build system. required-features is used
+# to disable it for regular builds.
+name = "y"
+path = "./y.rs"
+required-features = ["__check_build_system_using_ra"]
+
 [lib]
 crate-type = ["dylib"]
 
@@ -40,6 +47,7 @@ smallvec = "1.8.1"
 unstable-features = ["jit", "inline_asm"]
 jit = ["cranelift-jit", "libloading"]
 inline_asm = []
+__check_build_system_using_ra = []
 
 [package.metadata.rust-analyzer]
 rustc_private = true