tree 391b00b81181c2efa254dbe346dc2dbb20432577
parent eb97a6e7a1afa6d4817545bec3304e906ecc35f7
author Colin Cross <ccross@android.com> 1450299821 -0800
committer Colin Cross <ccross@android.com> 1450299821 -0800

Add optional_subdirs variable support

When building a subset of a source tree, some of the subdirectories
mentioned in the subdirs variable may be missing.  Add support for an
optional_subdirs variable, which won't error out if the requested
directory is missing.