Add build targets for constructing the Bazel.io Jekyll tree.

This patch adds pkg_tar build targets to site/, which can be used to combine
the Jekyll files under site/ with static Bootstrap and Font Awesome resources
under third_party.

Combining the site files with the generated Build Encyclopedia and Skylark
Library documentation will be done in a future change.

--
MOS_MIGRATED_REVID=121654239
diff --git a/site/BUILD b/site/BUILD
index 3683386..2cc9736 100644
--- a/site/BUILD
+++ b/site/BUILD
@@ -1,3 +1,5 @@
+load("@bazel_tools//tools/build_defs/pkg:pkg.bzl", "pkg_tar")
+
 exports_files(
     ["docs/bazel-user-manual.html"],
 )
@@ -7,3 +9,68 @@
     srcs = glob(["**"]),
     visibility = ["//:__pkg__"],
 )
+
+filegroup(
+    name = "jekyll-srcs",
+    srcs = glob(
+        ["**/*"],
+        exclude = [
+            "BUILD",
+            "jekyll-tree.sh",
+            "*.swp",
+        ],
+    ),
+)
+
+pkg_tar(
+    name = "jekyll-files",
+    files = [":jekyll-srcs"],
+    strip_prefix = ".",
+)
+
+pkg_tar(
+    name = "bootstrap-css",
+    files = ["//third_party/css/bootstrap:bootstrap_css"],
+    package_dir = "assets",
+    strip_prefix = "/third_party/css/bootstrap",
+)
+
+pkg_tar(
+    name = "bootstrap-images",
+    files = ["//third_party/css/bootstrap:bootstrap_images"],
+    package_dir = "assets",
+    strip_prefix = "/third_party/css/bootstrap",
+)
+
+pkg_tar(
+    name = "font-awesome-css",
+    files = ["//third_party/css/font_awesome:font_awesome_css"],
+    package_dir = "assets",
+    strip_prefix = "/third_party/css/font_awesome",
+)
+
+pkg_tar(
+    name = "font-awesome-font",
+    files = ["//third_party/css/font_awesome:font_awesome_font"],
+    package_dir = "assets",
+    strip_prefix = "/third_party/css/font_awesome",
+)
+
+pkg_tar(
+    name = "bootstrap-js",
+    files = ["//third_party/javascript/bootstrap:bootstrap_js"],
+    package_dir = "assets",
+    strip_prefix = "/third_party/javascript/bootstrap",
+)
+
+pkg_tar(
+    name = "jekyll-tree",
+    deps = [
+        ":bootstrap-css",
+        ":bootstrap-images",
+        ":bootstrap-js",
+        ":font-awesome-css",
+        ":font-awesome-font",
+        ":jekyll-files",
+    ],
+)
diff --git a/third_party/css/bootstrap/BUILD b/third_party/css/bootstrap/BUILD
index 18fc491..42c7a9d 100644
--- a/third_party/css/bootstrap/BUILD
+++ b/third_party/css/bootstrap/BUILD
@@ -9,14 +9,16 @@
 filegroup(
     name = "bootstrap_css",
     srcs = [
-        "css/boostrap.css",
-        "css/boostrap.css.map",
+        "css/bootstrap.css",
+        "css/bootstrap.css.map",
         "css/bootstrap.min.css",
         "css/bootstrap.min.css.map",
     ],
+    visibility = ["//site:__pkg__"],
 )
 
 filegroup(
     name = "bootstrap_images",
-    srcs = glob(["glyphicons-halflings-regular.*"]),
+    srcs = glob(["fonts/glyphicons-halflings-regular.*"]),
+    visibility = ["//site:__pkg__"],
 )
diff --git a/third_party/css/font_awesome/BUILD b/third_party/css/font_awesome/BUILD
index 129178c..a58e75e 100644
--- a/third_party/css/font_awesome/BUILD
+++ b/third_party/css/font_awesome/BUILD
@@ -12,9 +12,11 @@
         "css/font-awesome.css",
         "css/font-awesome.min.css",
     ],
+    visibility = ["//site:__pkg__"],
 )
 
 filegroup(
     name = "font_awesome_font",
     srcs = glob(["fonts/fontawesome-webfont.*"]),
+    visibility = ["//site:__pkg__"],
 )
diff --git a/third_party/javascript/bootstrap/BUILD b/third_party/javascript/bootstrap/BUILD
index 7253a6f..3b2f781 100644
--- a/third_party/javascript/bootstrap/BUILD
+++ b/third_party/javascript/bootstrap/BUILD
@@ -12,4 +12,5 @@
         "js/bootstrap.js",
         "js/bootstrap.min.js",
     ],
+    visibility = ["//site:__pkg__"],
 )