Chi Wang

According to the stack trace: ``` java.io.IOException: /private/var/tmp/_bazel_iosci/7c81b0540945e51fddc7bd01ee8d0abb/execroot/lyftios/bazel-out/darwin-fastbuild/bin/tools/CodeAnalysis/Tests/LinuxMain.swift.tmp (Not a directory) | at com.google.devtools.build.lib.unix.NativePosixFiles.openWrite(Native Method) | at com.google.devtools.build.lib.unix.UnixFileSystem.createFileOutputStream(UnixFileSystem.java:493) | at com.google.devtools.build.lib.vfs.AbstractFileSystem.getOutputStream(AbstractFileSystem.java:174) | at com.google.devtools.build.lib.vfs.AbstractFileSystem.getOutputStream(AbstractFileSystem.java:188) | at com.google.devtools.build.lib.vfs.Path.getOutputStream(Path.java:425) | at com.google.devtools.build.lib.vfs.Path.getOutputStream(Path.java:413)...

Might related https://github.com/bazelbuild/bazel/issues/6393.

@brentleyjones Is that possible to create a repro?

It's weird, the parent directories are actually [created](https://github.com/bazelbuild/bazel/blob/c2a9395324410bd301e024e57cc7c0bb0654c41d/src/main/java/com/google/devtools/build/lib/remote/RemoteCache.java#L355) before the download.

I am not aware of any bugs this fixes. but should be easy to cherry-pick into 5.3 if time allows.

I will take a look but I am not entire sure whether this can be fixed. Part of https://github.com/bazelbuild/bazel/commit/db15e47d0391d904c29e6e5c632089e2479e62c2 is to implement #13166 which by design needs lock (or similar)...

Made a small improvement via #16118 but still the regression is not able to fix since we need lock for every inputs to deduplicate `findMissingBlobs` calls and share uploads by...

No, I think we didn't verity it on Windows.

In theory Piston can run on Android/iOS because it use SDL2 as back-end but we haven't do it. One of the goal of Piston is support multi platform including mobile/tablet

A temporary fix applied. Moving down to P1.