racket/runtime-path: add support for 'share paths

Support include-if-exists for files in the "share" directory analogous
to the include-if-exists support for files in "lib".

pkgs/compiler-test/tests/compiler/embed/embed-me38.rkt

@@ -0,0 +1,12 @@
+#lang racket/base
+(require racket/runtime-path
+         (for-syntax racket/base))
+
+(define-runtime-path license '(share "LICENSE-libscheme.txt"))
+
+(if (absolute-path? license)
+    "found license"
+    "not found")
+
+
+

pkgs/compiler-test/tests/compiler/embed/test.rkt

@@ -272,7 +272,8 @@
     (one-mz-test "embed-me31.rkt" "This is 31.\n" #f)
     (one-mz-test "embed-me34.rkt" "This is 34 in a second place.\n" #f)
     (one-mz-test "embed-me35.rkt" "'ok-35\n" #f)
-    (one-mz-test "embed-me36.rkt" "'ok-36\n" #f))
+    (one-mz-test "embed-me36.rkt" "'ok-36\n" #f)
+    (one-mz-test "embed-me38.rkt" "\"found license\"\n" #f))
 
   ;; Try unicode expr and cmdline:
   (prepare dest "unicode")

pkgs/racket-doc/scribblings/reference/filesystem.scrbl

@@ -728,6 +728,14 @@ a platform-specific shared-library extension---as produced by
 @racket[(system-type 'so-suffix)]. A @racket[_vers]
 can be a string, or it can be a list of strings and @racket[#f].
 
+If @racket[expr] produces a list of the form @racket[(list 'share
+_str)], the value bound to @racket[id] can be either @racket[_str] or
+an absolute path; it is an absolute path when searching in the
+directories reported by @racket[find-user-share-dir] and
+@racket[find-share-dir] (in that order) locates the path. In this way,
+files that are installed in Racket's @filepath{share} directory get
+carried along in distributions.
+
 If @racket[expr] produces a list of the form @racket[(list 'module
 _module-path _var-ref)] or @racket[(list 'so _str (list
 _str-or-false ...))], the value bound to @racket[id] is a
@@ -798,7 +806,8 @@ In the latter two cases, the path is normally preserved in
 result of @racket[collection-file-path], then the path is record as
 relative to the corresponding module path.
 
-@history[#:changed "6.0.1.6" @elem{Preserve relative paths only within a package.}]
+@history[#:changed "6.0.1.6" @elem{Preserve relative paths only within a package.}
+         #:changed "7.5.0.7" @elem{Added support for @racket['share] in @racket[expr].}]
 
 Examples:
 

racket/collects/compiler/embed.rkt

@@ -13,6 +13,7 @@
          setup/collects
          file/ico
          racket/private/so-search
+         racket/private/share-search
          setup/cross-system
          "private/winsubsys.rkt"
          "private/macfw.rkt"
@@ -1306,6 +1307,7 @@
 									 ;; record the whole DLL in the executable
 									 #f]
 									[else path])]
+                                                                     [(share-spec? p) (share-find p)]
                                                                      [(and (list? p)
                                                                            (eq? 'lib (car p)))
                                                                       (let ([p (if (null? (cddr p))

racket/collects/racket/private/share-search.rkt

@@ -0,0 +1,21 @@
+#lang racket/base
+(require setup/dirs)
+
+(provide share-spec? share-find)
+
+(define (share-spec? p)
+  (and (list? p)
+       (= 2 (length p))
+       (eq? 'share (car p))
+       (string? (cadr p))))
+
+(define (share-find p)
+  (define f (cadr p))
+  (define (search dir)
+    (and dir
+         (let ([p (build-path dir f)])
+           (and (or (file-exists? p)
+                    (directory-exists? p))
+                p))))
+  (or (search (find-user-share-dir))
+      (search (find-share-dir))))

racket/collects/racket/runtime-path.rkt

@@ -4,6 +4,7 @@
 
 (require racket/list
          "private/so-search.rkt"
+         "private/share-search.rkt"
          "private/this-expression-source-directory.rkt"
          (only-in "private/runtime-path-table.rkt" table)
          (for-syntax racket/base))
@@ -97,6 +98,8 @@
               [(path? p) p]
               [(so-spec? p) (or (so-find p)
                                 (cadr p))]
+              [(share-spec? p) (or (share-find p)
+                                   (cadr p))]
               [(and (list? p)
                     ((length p) . > . 1)
                     (eq? 'lib (car p))