Add include_extensions to InstallDir Options (#17300)

closes #16687

Author: der-teufel-programming

lib/std/Build/Step/InstallDir.zig

@@ -21,6 +21,10 @@ pub const Options = struct {
     /// File paths which end in any of these suffixes will be excluded
     /// from being installed.
     exclude_extensions: []const []const u8 = &.{},
+    /// Only file paths which end in any of these suffixes will be included
+    /// in installation. `null` means all suffixes are valid for this option.
+    /// `exclude_extensions` take precedence over `include_extensions`
+    include_extensions: ?[]const []const u8 = null,
     /// File paths which end in any of these suffixes will result in
     /// empty files being installed. This is mainly intended for large
     /// test.zig files in order to prevent needless installation bloat.
@@ -34,6 +38,7 @@ pub const Options = struct {
             .install_dir = self.install_dir.dupe(b),
             .install_subdir = b.dupe(self.install_subdir),
             .exclude_extensions = b.dupeStrings(self.exclude_extensions),
+            .include_extensions = if (self.include_extensions) |incs| b.dupeStrings(incs) else null,
             .blank_extensions = b.dupeStrings(self.blank_extensions),
         };
     }
@@ -78,6 +83,16 @@ fn make(step: *Step, prog_node: *std.Progress.Node) !void {
                 continue :next_entry;
             }
         }
+        if (self.options.include_extensions) |incs| {
+            var found = false;
+            for (incs) |inc| {
+                if (mem.endsWith(u8, entry.path, inc)) {
+                    found = true;
+                    break;
+                }
+            }
+            if (!found) continue :next_entry;
+        }
 
         // relative to src build root
         const src_sub_path = try fs.path.join(arena, &.{ src_dir_path, entry.path });