Building just built workspace results in recompilation of java.base and increase in build time.

$ make LOG=info
Generating main target list
Running make as 'make LOG=info'
Building target 'default' in configuration 'windows-x86_64-normal-server-release'
Linking executable genSocketOptionRegistry.exe
Microsoft (R) Incremental Linker Version 12.00.30723.0
Copyright (C) Microsoft Corporation. All rights reserved.

Compiling 2803 files for java.base
Stopping sjavac server
----- Build times -------
Start 2016-02-27 12:26:52
End 2016-02-27 12:27:37

00:00:45 TOTAL
-------------------------
Finished building target 'default' in configuration 'windows-x86_64-normal-server-release'

Last working in b102, debug logs are attached.