fix(package): Don't let case-insensitivty to get in the way

src/cargo/util/toml/targets.rs

@@ -628,7 +628,7 @@ fn resolve_targets_with_legacy_path(
 fn inferred_lib(package_root: &Path) -> Option<PathBuf> {
     let lib = Path::new("src").join("lib.rs");
     if package_root.join(&lib).exists() {
-        Some(lib)
+        Some(normalize_case(package_root, &lib))
     } else {
         None
     }
@@ -638,7 +638,7 @@ fn inferred_bins(package_root: &Path, package_name: &str) -> Vec<(String, PathBu
     let main = "src/main.rs";
     let mut result = Vec::new();
     if package_root.join(main).exists() {
-        let main = PathBuf::from(main);
+        let main = normalize_case(package_root, Path::new(main));
         result.push((package_name.to_string(), main));
     }
     let default_bin_dir_name = Path::new("src").join("bin");
@@ -1046,7 +1046,12 @@ pub fn resolve_build(build: Option<&StringOrBool>, package_root: &Path) -> Optio
             // a build script.
             let build_rs = package_root.join(BUILD_RS);
             if build_rs.is_file() {
-                Some(StringOrBool::String(BUILD_RS.to_owned()))
+                let build_rs = normalize_case(package_root, Path::new(BUILD_RS));
+                let build_rs = build_rs
+                    .into_os_string()
+                    .into_string()
+                    .unwrap_or_else(|_| BUILD_RS.to_owned());
+                Some(StringOrBool::String(build_rs))
             } else {
                 Some(StringOrBool::Bool(false))
             }
@@ -1057,6 +1062,18 @@ pub fn resolve_build(build: Option<&StringOrBool>, package_root: &Path) -> Optio
     }
 }
 
+fn normalize_case(package_root: &Path, rel_path: &Path) -> PathBuf {
+    try_normalize_case(package_root, rel_path).unwrap_or_else(|| rel_path.to_owned())
+}
+
+fn try_normalize_case(package_root: &Path, rel_path: &Path) -> Option<PathBuf> {
+    let path = package_root.join(rel_path);
+    let path = path.canonicalize().ok()?;
+    let package_root = package_root.canonicalize().ok()?;
+    let rel_path = path.strip_prefix(&package_root).ok()?;
+    Some(rel_path.to_owned())
+}
+
 fn name_or_panic(target: &TomlTarget) -> &str {
     target
         .name