build: Use flock to serialize ar steps as workaround

[xiaoxiang781216]

Use flock to serialize ar steps to avoid parallel build break
sometimes.

Change-Id: I3a916b3b27422cdb6d718f7d554361565457fa08
Signed-off-by: Xiang Xiao xiaoxiang@xiaomi.com

[xiaoxiang781216]

A general version of:
apache/nuttx#102
Before we get a better solution, this patch can fix the parallel build which is very important for the upcoming Apache Jenkins and Github Action.

[xiaoxiang781216]

@masayuki2009 please associate your github account with apache account:
https://whimsy.apache.org/roster/ppmc/nuttx
so I can add you to reviewer list.

[masayuki2009]

@masayuki2009 please associate your github account with apache account:
https://whimsy.apache.org/roster/ppmc/nuttx
so I can add you to reviewer list.

@xiaoxiang781216 I'll setup it later.

[masayuki2009]

@xiaoxiang781216 I've just added my github account info to the apache.

[yamt]

macOS doesn't have flock.
how about using shlock instead? macOS has it.

[xiaoxiang781216]

macOS doesn't have flock.
how about using shlock instead? macOS has it.

But shlock doesn't exist on cygwin and msys2, even Ubuntu need install manually with apt-get install:(.

[xiaoxiang781216]

How about https://github.com/discoteq/flock:
brew tap discoteq/discoteq
brew install flock

[masayuki2009]

@xiaoxiang781216 It looks good to me.

[patacongo]

How about https://github.com/discoteq/flock:
brew tap discoteq/discoteq
brew install flock

This would need to be documented so macOS users would have to install flock? I will merge this PR when the documentation updates are in place. This should be covered in the top-level README.txt file.

[xiaoxiang781216]

@patacongo here is the patch updating README.txt:
apache/nuttx#337

[masayuki2009]

Hi, @xiaoxiang781216,

I found that this solution still has a problem.
Because .arlock files are created in each application directory.

I think the lock file should be in the same directory as '.a' file,
because we want to protect '.a' file access.

Or as I tried before, the lock file could be at the top directory. (rather giant lock)

[xiaoxiang781216]

Hi, @xiaoxiang781216,

I found that this solution still has a problem.
Because .arlock files are created in each application directory.

I think the lock file should be in the same directory as '.a' file, because we want to protect '.a' file access.

Or as I tried before, the lock file could be at the top directory. (rather giant lock)

Yes, I will send a new PR fix this issue.

[xiaoxiang781216]

@masayuki2009 see this:
#80