Store build_date in .tizen.build-id section to avoid unnecessary rebuilds

Store build_date in .tizen.build-id section to avoid unnecessary rebuilds

- PROBLEM
We use OBS to build packages in Tizen.
There is a mechanism not to rebuild if the result binary is the same.
For example, there is a dependency graph: A->B->C.
If A is modified, B would be built.
If the result RPM of B is not changed, OBS does not trigger a build of C.
To effectively use this mechanism, each packages make sure that
the result binary should be the same if the input source is the same.

This package uses __DATE__ and __TIME__ which make the result binary
is different everytime it is built.
To efficiently utilize OBS build mechanism and to modify the package
as little as possible, I propose to store this macro in .tizen.build-id
section. OBS build-compare tool does not check *.build-id section
in the binary.

Change-Id: Icc1b62f5f56506d64deae3a5fadabb82eca6f1e6
Signed-off-by: Junghyun Kim <jh0822.kim@samsung.com>