Add rustc version info (git hash + date) to dist tarball

fixes #32444

mk/dist.mk

@@ -76,6 +76,7 @@ tmp/dist/$$(SRC_PKG_NAME)-image: $(PKG_FILES)
 	@$(call E, making src image)
 	$(Q)rm -Rf tmp/dist/$(SRC_PKG_NAME)-image
 	$(Q)mkdir -p tmp/dist/$(SRC_PKG_NAME)-image/lib/rustlib/src/rust
+	$(Q)echo "$(CFG_VERSION)" > tmp/dist/$(SRC_PKG_NAME)-image/lib/rustlib/src/rust/version
 	$(Q)tar \
          -C $(S) \
          -f - \

src/bootstrap/dist.rs

@@ -388,6 +388,9 @@ pub fn rust_src(build: &Build) {
     // Rename directory, so that root folder of tarball has the correct name
     t!(fs::rename(&dst_src, &plain_dst_src));
 
+    // Create the version file
+    write_file(&plain_dst_src.join("version"), build.version.as_bytes());
+
     // Create plain source tarball
     let mut cmd = Command::new("tar");
     cmd.arg("-czf").arg(sanitize_sh(&distdir(build).join(&format!("{}.tar.gz", plain_name))))
@@ -431,3 +434,8 @@ fn sanitize_sh(path: &Path) -> String {
         Some(format!("/{}/{}", drive, &s[drive.len_utf8() + 2..]))
     }
 }
+
+fn write_file(path: &Path, data: &[u8]) {
+    let mut vf = t!(fs::File::create(path));
+    t!(vf.write_all(data));
+}