xtask: Add --lcov switch to the coverage action

This will be used to provide raw coverage data for the CI job.

xtask/src/cargo.rs

@@ -187,6 +187,7 @@ pub enum CargoAction {
     Build,
     Clippy,
     Coverage {
+        lcov: bool,
         open: bool,
     },
     Doc {
@@ -254,9 +255,13 @@ impl Cargo {
                     tool_args.extend(["-D", "warnings"]);
                 }
             }
-            CargoAction::Coverage { open } => {
+            CargoAction::Coverage { lcov, open } => {
                 action = "llvm-cov";
-                extra_args.push("--html");
+                if lcov {
+                    extra_args.extend(["--lcov", "--output-path", "target/llvm-cov/lcov"]);
+                } else {
+                    extra_args.push("--html");
+                }
                 if open {
                     extra_args.push("--open");
                 }

xtask/src/main.rs

@@ -89,7 +89,7 @@ fn clippy(opt: &ClippyOpt) -> Result<()> {
 fn code_coverage(opt: &CovOpt) -> Result<()> {
     if has_cmd("cargo-llvm-cov") {
         let cargo = Cargo {
-            action: CargoAction::Coverage { open: opt.open },
+            action: CargoAction::Coverage { lcov: opt.lcov, open: opt.open },
             features: Feature::more_code(*opt.unstable, false),
             // Leave out uefi-macros; the compilation tests will just make
             // things slower without contributing anything to the coverage

xtask/src/opt.rs

@@ -113,6 +113,10 @@ pub struct CovOpt {
     #[clap(long, action)]
     pub open: bool,
 
+    /// Output raw lcov data instead of HTML.
+    #[clap(long, action, conflicts_with = "open")]
+    pub lcov: bool,
+
     #[clap(flatten)]
     pub unstable: UnstableOpt,
 }