Bugfix/crt static in config

src/cargo/core/compiler/build_context/mod.rs

@@ -345,7 +345,12 @@ fn env_args(
             .map(str::trim)
             .filter(|s| !s.is_empty())
             .map(str::to_string);
-        return Ok(args.collect());
+
+        let rustflags: Vec<_> = args.collect();
+
+        if rustflags.len() > 0 {
+            return Ok(rustflags);
+        }
     }
 
     let mut rustflags = Vec::new();

tests/testsuite/rustflags.rs

@@ -1359,3 +1359,122 @@ fn env_rustflags_misspelled_build_script() {
         .with_stderr_contains("[WARNING] Cargo does not read `RUST_FLAGS` environment variable. Did you mean `RUSTFLAGS`?")
         .run();
 }
+
+#[test]
+fn env_rustflags_with_crt_static_sets_env_var() {
+    // The CARGO_CFG_TARGET_FEATURE env var should be set when passing this flag.
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            build = "build.rs"
+        "#,
+        )
+        .file("src/lib.rs", "")
+        .file(
+            "build.rs",
+            r#"
+            fn main() {
+                // The crt-static feature should be enabled.
+                #[cfg(not(target_feature = "crt-static"))]
+                assert!(false);
+
+                assert!(std::env::var("CARGO_CFG_TARGET_FEATURE").unwrap().contains("crt-static"));
+            }
+        "#,
+        )
+        .build();
+
+    p.cargo("build")
+        .env("RUSTFLAGS", "-Ctarget-feature=+crt-static")
+        .run();
+}
+
+#[test]
+fn config_rustflags_with_crt_static_sets_env_var() {
+    // The CARGO_CFG_TARGET_FEATURE env var should be set when passing this flag using a config file.
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            build = "build.rs"
+        "#,
+        )
+        .file(
+            ".cargo/config",
+            r#"
+            [build]
+            rustflags = [
+                "-Ctarget-feature=+crt-static",
+            ]
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .file(
+            "build.rs",
+            r#"
+            fn main() {
+                // The crt-static feature should be enabled.
+                #[cfg(not(target_feature = "crt-static"))]
+                assert!(false);
+
+                assert!(std::env::var("CARGO_CFG_TARGET_FEATURE").unwrap().contains("crt-static"));
+            }
+        "#,
+        )
+        .build();
+
+    p.cargo("build")
+        .env("RUSTFLAGS", "")
+        .run();
+}
+
+#[test]
+fn config_rustflags_with_target_filter_with_crt_static_sets_env_var() {
+    // The CARGO_CFG_TARGET_FEATURE env var should be set when passing this flag using a config file.
+    let p = project()
+        .file(
+            "Cargo.toml",
+            r#"
+            [package]
+            name = "foo"
+            version = "0.0.1"
+            edition = "2018"
+            build = "build.rs"
+        "#,
+        )
+        .file(
+            ".cargo/config",
+            r#"
+            [target.'cfg(target_arch="x86_64")']
+            rustflags = [
+                "-Ctarget-feature=+crt-static",
+            ]
+            "#,
+        )
+        .file(
+            "src/main.rs",
+            r#"fn main() {}"#,
+        )
+        .file(
+            "build.rs",
+            r#"use std::env;
+            fn main() {
+                // The crt-static feature should be enabled.
+                #[cfg(not(target_feature = "crt-static"))]
+                assert!(false);
+
+                assert!(std::env::var("CARGO_CFG_TARGET_FEATURE").unwrap().contains("crt-static"));
+            }
+        "#,
+        )
+        .build();
+
+    p.cargo("build").run();
+}