coverage: Tell llvm-cov to show branch information

Author: Zalathar

src/tools/compiletest/src/runtest.rs

@@ -565,7 +565,12 @@ impl<'test> TestCx<'test> {
 
         // Run `llvm-cov show` to produce a coverage report in text format.
         let proc_res = self.run_llvm_tool("llvm-cov", |cmd| {
-            cmd.args(["show", "--format=text", "--show-line-counts-or-regions"]);
+            cmd.args([
+                "show",
+                "--format=text",
+                "--show-line-counts-or-regions",
+                "--show-branches=count",
+            ]);
 
             cmd.arg("--Xdemangler");
             cmd.arg(self.config.rust_demangler_path.as_ref().unwrap());