trim correctly (#8388)

Co-authored-by: dave caruso <me@paperdave.net>
Co-authored-by: Jarred Sumner <jarred@jarredsumner.com>

src/resolver/package_json.zig

@@ -1135,6 +1135,7 @@ pub const ExportsMap = struct {
                         map_data_ranges[i] = key_range;
                         map_data_entries[i] = this.visit(prop.value.?);
 
+                        // safe to use "/" on windows. exports in package.json does not use "\\"
                         if (strings.endsWithComptime(key, "/") or strings.containsChar(key, '*')) {
                             expansion_keys[expansion_key_i] = Entry.Data.Map.MapEntry{
                                 .value = map_data_entries[i],

src/resolver/resolver.zig

@@ -2251,13 +2251,13 @@ pub const Resolver = struct {
     fn handleESMResolution(r: *ThisResolver, esm_resolution_: ESModule.Resolution, abs_package_path: string, kind: ast.ImportKind, package_json: *PackageJSON, package_subpath: string) ?MatchResult {
         var esm_resolution = esm_resolution_;
         if (!((esm_resolution.status == .Inexact or esm_resolution.status == .Exact or esm_resolution.status == .ExactEndsWithStar) and
-            esm_resolution.path.len > 0 and esm_resolution.path[0] == '/'))
+            esm_resolution.path.len > 0 and esm_resolution.path[0] == std.fs.path.sep))
             return null;
 
         const abs_esm_path: string = brk: {
             var parts = [_]string{
                 abs_package_path,
-                strings.withoutLeadingSlash(esm_resolution.path),
+                strings.withoutLeadingPathSeparator(esm_resolution.path),
             };
             break :brk r.fs.absBuf(&parts, bufs(.esm_absolute_package_path_joined));
         };

src/string_immutable.zig

@@ -698,6 +698,10 @@ pub fn withoutLeadingSlash(this: string) []const u8 {
     return std.mem.trimLeft(u8, this, "/");
 }
 
+pub fn withoutLeadingPathSeparator(this: string) []const u8 {
+    return std.mem.trimLeft(u8, this, &.{std.fs.path.sep});
+}
+
 pub fn endsWithAny(self: string, str: string) bool {
     const end = self[self.len - 1];
     for (str) |char| {