Make app shims launch without a DYLD_LIBRARY_PATH.

App shims from a component build previously wouldn't launch without the
DYLD_LIBRARY_PATH environment variable set to the path to the out directory.
This change embeds the path so that they can be launched normally.

Change-Id: I5c88b0e70172d385d93e8de8d096b03ea408d942
Reviewed-on: https://chromium-review.googlesource.com/c/1393533Reviewed-by: ccameron <ccameron@chromium.org>
Commit-Queue: Sidney San Martín <sdy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#619648}

chrome/app_shim/BUILD.gn

@@ -55,6 +55,16 @@ mac_app_bundle("app_mode_loader") {
     "app_mode_loader_mac.mm",
   ]
 
+  if (is_component_build) {
+    # Loaders are installed to ~/Applications. In a component build, include
+    # the absolute path to the out dir in their library search path so that
+    # their components are found at launch.
+    ldflags = [
+      "-rpath",
+      rebase_path(root_out_dir),
+    ]
+  }
+
   deps = [
     "//base",
     "//chrome/common:app_mode_app_support",