This patch does not create right result.

This patch does not create right result.
When we run gl application, we expect the result like as
"  [CoreGL] <1004> (Sat Aug 27 11:08:17 UTC 2016) Library initializing... [CoreGL] Driver GL version 3.2  "

but this patch shows "  [CoreGL] <1026> (fatal: Not a git repository (or any of the parent directories): .git) Library initializing... [CoreGL] Driver GL version 3.2 "

so we should fix it

Revert "build: Use commit date instead of build date to avoid unnecessary rebuilds."

This reverts commit c74c199cfbab5d54dad0046b0d747ace552aebe4.

Change-Id: I370d5ea701bd6635be1b99972607c5fff6fbfd58