scribble/manual: delay expressions that require collection-based files

This changed make `(require scribble/manual)` work in an executable,
although actually rendering documents requires the "scribble"
collection.

original commit: 9ca0aa52250c18dd05c2a19bea654ca770aecf0c

pkgs/scribble-pkgs/scribble-lib/scribble/private/manual-defaults.rkt

@@ -1,7 +1,8 @@
 #lang scheme/base
 (require scribble/core
          scribble/html-properties
-         "defaults.rkt")
+         "defaults.rkt"
+         "on-demand.rkt")
 
 (provide post-process
          manual-doc-style)
@@ -20,5 +21,5 @@
                                (scribble-file "manual-racket.css")))
                 #t))
 
-(define manual-doc-style
+(define-on-demand manual-doc-style
   (part-style (post-process (part #f null #f plain null null null))))

pkgs/scribble-pkgs/scribble-lib/scribble/private/manual-scheme.rkt

@@ -7,6 +7,7 @@
          (only-in "../core.rkt" style style-properties)
          "manual-style.rkt"
          "manual-utils.rkt" ;; used via datum->syntax
+         "on-demand.rkt"
          (for-syntax racket/base)
          (for-label racket/base))
 
@@ -211,7 +212,7 @@
       (*as-modname-link s e indirect?)
       e))
 
-(define indirect-module-link-color
+(define-on-demand indirect-module-link-color
   (struct-copy style module-link-color
                [properties (cons 'indirect-link
                                  (style-properties module-link-color))]))

pkgs/scribble-pkgs/scribble-test/tests/scribble/exe.rkt

@@ -0,0 +1,33 @@
+#lang racket/base
+(require racket/file
+         compiler/embed
+         racket/system)
+
+;; Check that `scribble/manual` can be embedded in an executable
+
+(define src (make-temporary-file))
+(define exe (make-temporary-file))
+
+(call-with-output-file src
+  #:exists 'truncate
+  (lambda (o)
+    (write '(module m racket/base
+              (require scribble/manual))
+           o)))
+
+(define mod-sym (string->symbol
+                 (format "~a"
+                         (let-values ([(base name dir?)
+                                       (split-path src)])
+                           (path->bytes (path-replace-suffix name #""))))))
+
+(create-embedding-executable exe
+                             #:cmdline '("-U")
+                             #:collects-path null
+                             #:modules `((#f ,src))
+                             #:configure-via-first-module? #t
+                             #:literal-expression
+                             (parameterize ([current-namespace (make-base-namespace)])
+                               (compile `(namespace-require '',mod-sym))))
+
+(system* exe)