[ios/goma] Create symlinks to Xcode SDK in $root_build_dir/sdk

Creating symlinks in src/ can mess with the build because some
scripts incorrectly re-invoke `gn gen` as part of the build.

Also, it does not make sense to create symlinks in src/ based
on a gn variable that can have different value for different
build directories.

Bug: 1060666, 1061419
Change-Id: I2367aa6436489b77540454da8f7ae17d41c6f9fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2102649
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#750187}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 909de78b93850db4371465c23d4593fdda93c8c4

.gitignore

@@ -22,6 +22,5 @@ ciopfs
 /linux/ubuntu_*-sysroot/
 /ios_files
 /mac_files
-/xcode_links
 
 !/util/LASTCHANGE.dummy

config/ios/ios_sdk.gni

@@ -106,7 +106,10 @@ if (ios_sdk_path == "") {
     ]
   }
   if (ios_use_goma_rbe) {
-    ios_sdk_info_args += [ "--create_symlink_under_src" ]
+    ios_sdk_info_args += [
+      "--create_symlink_at",
+      rebase_path("$root_build_dir/sdk/xcode_links", "//"),
+    ]
   }
   script_name = "//build/config/mac/sdk_info.py"
   _ios_sdk_result = exec_script(script_name, ios_sdk_info_args, "scope")

config/mac/mac_sdk.gni

@@ -92,8 +92,9 @@ if (!use_system_xcode) {
 # put system xcode under src to avoid absolute path.
 if (use_system_xcode && ios_use_goma_rbe) {
   sdk_info_args += [
-    "--create_symlink_under_src",
     "--get_sdk_info",
+    "--create_symlink_at",
+    rebase_path("$root_build_dir/sdk/xcode_links", "//"),
   ]
 }
 sdk_info_args += [ mac_sdk_name ]

config/mac/sdk_info.py

@@ -108,39 +108,42 @@ def FillSDKPathAndVersion(settings, platform, xcode_version):
     settings['sdk_build'] = settings['sdk_version']
 
 
-def CreateXcodeSymlinkUnderChromiumSource(src):
-  """Create symlink to Xcode directory under Chromium source."""
+def CreateXcodeSymlinkAt(src, dst):
+  """Create symlink to Xcode directory at target location."""
 
-  if not os.path.isdir(XCODE_LINK_DIR):
-    os.makedirs(XCODE_LINK_DIR)
+  if not os.path.isdir(dst):
+    os.makedirs(dst)
+
+  dst = os.path.join(dst, os.path.basename(src))
+  updated_value = '//' + os.path.relpath(dst, ROOT_SRC_DIR)
 
-  dst = os.path.join(XCODE_LINK_DIR, os.path.basename(src))
   # Update the symlink only if it is different from the current destination.
   if os.path.islink(dst):
-    current_dst = os.readlink(src)
-    if current_dst != dst:
-      os.unlink(src)
-      sys.stderr.write('existing symlink %s points %s; want %s. Removed.' %
-                       (src, current_dst, dst))
+    current_src = os.readlink(dst)
+    if current_src == src:
+      return updated_value
+    os.unlink(dst)
+    sys.stderr.write('existing symlink %s points %s; want %s. Removed.' %
+                     (dst, current_src, src))
   os.symlink(src, dst)
-
-  return '//' + os.path.relpath(dst, ROOT_SRC_DIR)
+  return updated_value
 
 
 if __name__ == '__main__':
   doctest.testmod()
 
   parser = argparse.ArgumentParser()
-  parser.add_argument("--developer_dir", required=False)
+  parser.add_argument("--developer_dir", dest="developer_dir", required=False)
   parser.add_argument("--get_sdk_info",
                     action="store_true", dest="get_sdk_info", default=False,
                     help="Returns SDK info in addition to xcode/machine info.")
-  parser.add_argument("--create_symlink_under_src",
-                      action="store_true", dest="create_symlink_under_src",
-                      default=False,
-                      help="Create symlink of SDK under Chromium source "
-                      "and returns the symlinked paths as SDK info instead "
-                      "of the original location.")
+  parser.add_argument(
+      "--create_symlink_at",
+      action="store",
+      dest="create_symlink_at",
+      help="Create symlink of SDK at given location and "
+      "returns the symlinked paths as SDK info instead "
+      "of the original location.")
   args, unknownargs = parser.parse_known_args()
   if args.developer_dir:
     os.environ['DEVELOPER_DIR'] = args.developer_dir
@@ -159,8 +162,8 @@ if __name__ == '__main__':
 
   for key in sorted(settings):
     value = settings[key]
-    if args.create_symlink_under_src and '_path' in key:
-      value = CreateXcodeSymlinkUnderChromiumSource(value)
+    if args.create_symlink_at and '_path' in key:
+      value = CreateXcodeSymlinkAt(value, args.create_symlink_at)
     if isinstance(value, str):
       value = '"%s"' % value
     print('%s=%s' % (key, value))