Let ninja/n2 do the configure invocation

I'd introduced maybe_reconfigure_build() after running into issues where
configure was not being invoked, but have discovered why that was happening:
the out folder path must be identical to the canonical path listed in
build.ninja, which it wasn't when a symlink was used. With this change,
we avoid having to invoke ninja twice, and get visibility into the
configure step.

This also makes rsbridge only depend on out/env, which prevents it from
being rebuilt when any reconfigure happens.

build/configure/src/rust.rs

@@ -115,7 +115,7 @@ fn build_rsbridge(build: &mut Build) -> Result<()> {
                 ":rslib:i18n",
                 ":rslib:proto",
                 // when env vars change the build hash gets updated
-                "$builddir/build.ninja",
+                "$builddir/env",
                 // building on Windows requires python3.lib
                 if cfg!(windows) {
                     inputs![":extract:python"]

build/ninja_gen/src/build.rs

@@ -50,7 +50,7 @@ impl Build {
             groups: Default::default(),
         };
 
-        build.add_action("build:run_configure", ConfigureBuild {})?;
+        build.add_action("build:configure", ConfigureBuild {})?;
 
         Ok(build)
     }

build/ninja_gen/src/configure.rs

@@ -19,7 +19,7 @@ impl BuildAction for ConfigureBuild {
     }
 
     fn files(&mut self, build: &mut impl FilesHandle) {
-        build.add_inputs("cmd", inputs![":build:configure"]);
+        build.add_inputs("cmd", inputs![":build:configure_bin"]);
         // reconfigure when external inputs change
         build.add_inputs("", inputs!["$builddir/env", ".version", ".git"]);
         build.add_outputs("", ["build.ninja"])
@@ -27,7 +27,7 @@ impl BuildAction for ConfigureBuild {
 
     fn on_first_instance(&self, build: &mut Build) -> Result<()> {
         build.add_action(
-            "build:configure",
+            "build:configure_bin",
             CargoBuild {
                 inputs: inputs![glob!["build/**/*"]],
                 outputs: &[RustOutput::Binary("configure")],
@@ -38,4 +38,12 @@ impl BuildAction for ConfigureBuild {
         )?;
         Ok(())
     }
+
+    fn generator(&self) -> bool {
+        true
+    }
+
+    fn check_output_timestamps(&self) -> bool {
+        true
+    }
 }

build/runner/src/build.rs

@@ -8,6 +8,7 @@ use std::process::Command;
 use std::time::Instant;
 
 use camino::Utf8Path;
+use camino::Utf8PathBuf;
 use clap::Args;
 use termcolor::Color;
 use termcolor::ColorChoice;
@@ -22,7 +23,7 @@ pub struct BuildArgs {
 }
 
 pub fn run_build(args: BuildArgs) {
-    let build_root = setup_build_root();
+    let build_root = &setup_build_root();
 
     let path = if cfg!(windows) {
         format!(
@@ -47,8 +48,6 @@ pub fn run_build(args: BuildArgs) {
     let build_file = build_root.join("build.ninja");
     if !build_file.exists() {
         bootstrap_build();
-    } else {
-        maybe_reconfigure_build(&build_file, &path);
     }
 
     // automatically convert foo:bar references to foo_bar, as Ninja can not
@@ -117,7 +116,7 @@ fn get_ninja_command() -> &'static str {
     }
 }
 
-fn setup_build_root() -> &'static Utf8Path {
+fn setup_build_root() -> Utf8PathBuf {
     let build_root = Utf8Path::new("out");
 
     #[cfg(unix)]
@@ -139,22 +138,10 @@ fn setup_build_root() -> &'static Utf8Path {
     }
 
     fs::create_dir_all(build_root).unwrap();
-
-    build_root
-}
-
-fn maybe_reconfigure_build(build_file: &Utf8Path, path: &str) {
-    let output = Command::new(get_ninja_command())
-        .arg("-f")
-        .arg(build_file)
-        .arg("build_run_configure")
-        .env("PATH", path)
-        .output()
-        .expect("ninja installed");
-    if !output.status.success() {
-        // The existing build.ninja may be invalid if files have been renamed/removed;
-        // resort to a slower cargo invocation instead to regenerate it.
-        bootstrap_build();
+    if cfg!(windows) {
+        build_root.to_owned()
+    } else {
+        build_root.canonicalize_utf8().unwrap()
     }
 }