Reland https://dart-review.googlesource.com/c/sdk/+/96500

Rather than creating the abiversions directory during gclient update,
check in an (almost) empty directory. This fixes the flutter build.

Bug: https://github.com/dart-lang/sdk/issues/36047
Change-Id: Ied74210bfc1c8fda998f58f754eac3949ebe0718
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/96846
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Liam Appelbe <liama@google.com>

sdk/BUILD.gn

@@ -495,6 +495,16 @@ copy("copy_vm_dill_files") {
   ]
 }
 
+copy("copy_abi_dill_files") {
+  visibility = [ ":create_common_sdk" ]
+  sources = [
+    "../tools/abiversions",
+  ]
+  outputs = [
+    "$root_out_dir/dart-sdk/lib/_internal/abiversions",
+  ]
+}
+
 copy("copy_dart2js_dill_files") {
   visibility = [ ":create_full_sdk" ]
   deps = [
@@ -889,6 +899,7 @@ copy("copy_api_readme") {
 group("create_common_sdk") {
   visibility = [ ":create_sdk" ]
   public_deps = [
+    ":copy_abi_dill_files",
     ":copy_analysis_summaries",
     ":copy_api_readme",
     ":copy_dart",

tools/.gitignore

@@ -1,4 +1,3 @@
-# tools/idl_parser and tools/abiversions are populated by gclient sync
-abiversions
+# tools/idl_parser is populated by gclient sync
 idl_parser
 

tools/abiversions/.gitignore

@@ -0,0 +1,4 @@
+# This directory is populated by gclient sync. But we still need the directory
+# to be checked in, and git doesn't track empty directories, hence this file.
+*
+!.gitignore

tools/download_abi_dills.py

@@ -13,6 +13,8 @@ def main():
   ensure_file = ''
   for i in xrange(oldest_abi_version, abi_version):
     ensure_file += '@Subdir %d\ndart/abiversions/%d latest\n\n' % (i, i)
+  if not ensure_file:
+    return 0
   p = subprocess.Popen(cmd,
                        stdin = subprocess.PIPE,
                        shell = utils.IsWindows(),