minor tweaks

Author: RalfJung

src/tools/miri/CONTRIBUTING.md

@@ -73,6 +73,7 @@ For example:
 You can (cross-)run the entire test suite using:
 
 ```sh
+./miri test
 ./miri test --target i686-unknown-linux-gnu
 ```
 

src/tools/miri/miri-script/src/commands.rs

@@ -491,10 +491,8 @@ impl Command {
             // Found it!
             e.sh.set_var("MIRI_TEST_TARGET", target);
 
-            let triple = target
-                .clone()
-                .into_string()
-                .map_err(|_| anyhow!("invalid target triple encoding"))?;
+            let triple =
+                target.clone().into_string().map_err(|_| anyhow!("target triple is not UTF-8"))?;
             Some(triple)
         } else if let Ok(target) = std::env::var("MIRI_TEST_TARGET") {
             // Convert `MIRI_TEST_TARGET` into `--target`.

src/tools/miri/miri-script/src/main.rs

@@ -87,7 +87,7 @@ Just build miri. <flags> are passed to `cargo build`.
 ./miri check <flags>:
 Just check miri. <flags> are passed to `cargo check`.
 
-./miri test [--bless] [--target] <flags>:
+./miri test [--bless] [--target <target>] <flags>:
 Build miri, set up a sysroot and then run the test suite. <flags> are passed
 to the test harness.
 
@@ -165,7 +165,7 @@ fn main() -> Result<()> {
                             let target_str = value
                                 .clone()
                                 .into_string()
-                                .map_err(|_| anyhow!("invalid target triple encoding"))?;
+                                .map_err(|_| anyhow!("target triple is not UTF-8"))?;
                             Some(target_str)
                         } else {
                             bail!("no target triple found")