Add NDK 25b to Windows BazelCI

[ahumesky]

To support tests for rules_android_ndk on Windows, we need an updated version of the NDK. Version 25b is on linux:

continuous-integration/buildkite/setup-docker.sh

Lines 166 to 175 in fcd3cdd

	### Install Android NDK.
	{
	cd /opt
	curl -fsSL -o android-ndk-r15c.zip https://dl.google.com/android/repository/android-ndk-r15c-linux-x86_64.zip
	unzip android-ndk-r15c.zip > /dev/null
	rm android-ndk-r15c.zip
	curl -fsSL -o android-ndk-r25b.zip https://dl.google.com/android/repository/android-ndk-r25b-linux.zip
	unzip android-ndk-r25b.zip > /dev/null
	rm android-ndk-r25b.zip
	}

So we should add Windows 25b to match. The URL is:
https://dl.google.com/android/repository/android-ndk-r25b-windows.zip

continuous-integration/buildkite/setup-windows.ps1

Lines 198 to 208 in fcd3cdd

	## Download the Android NDK and install into C:\android-ndk-r15c.
	$android_ndk_url = "https://dl.google.com/android/repository/android-ndk-r15c-windows-x86_64.zip"
	$android_ndk_zip = "c:\temp\android_ndk.zip"
	$android_ndk_root = "c:\android_ndk"
	New-Item $android_ndk_root -ItemType "directory" -Force
	(New-Object Net.WebClient).DownloadFile($android_ndk_url, $android_ndk_zip)
	[System.IO.Compression.ZipFile]::ExtractToDirectory($android_ndk_zip, $android_ndk_root)
	Rename-Item "${android_ndk_root}\android-ndk-r15c" -NewName "r15c"
	[Environment]::SetEnvironmentVariable("ANDROID_NDK_HOME", "${android_ndk_root}\r15c", "Machine")
	$env:ANDROID_NDK_HOME = [Environment]::GetEnvironmentVariable("ANDROID_NDK_HOME", "Machine")
	Remove-Item $android_ndk_zip

(NDK 26d is actually the lastest version of the NDK, but we should test and update to the latest version in a separate change.)

[meteorcloudy]

Merged #1965, I'll update the VM image now.

[meteorcloudy]

Windows VMs has been updated.

Android NDK r25b is installed to c:\android_ndk\r25b. However the default ANDROID_NDK_HOME env var still points to c:\android_ndk\r15c, you can override that in your presubmit.yml file.

[ahumesky]

Thank you!

[meteorcloudy]

Re-open since the image has been rolled back

[meteorcloudy]

I have a new Windows VM image in testing with the fix from #1968, will push next Monday morning.

[meteorcloudy]

The new image is pushed, let me know if there is any problem with the android ndk versions.