Partially revert BUILD_DATETIME change

Change Ibe4ceb1b224c5e8f3e1a8a59cfee89217765a901 caused kati to
regenerate on every build:
$(shell cat out/build_date.txt) was changed, regenerating...
Switch back to $(shell date +%s) which is special cased in kati
to not cause a regeneration.  Everything besides DATE will still
use BUILD_DATETIME_FROM_FILE from soong_ui.

Once BUILD_NUMBER is moved to soong_ui $(DATE) is no longer
necessary and the whole thing can be removed.

Bug: 70351683
Bug: 73352417
Test: m && m doesn't regenerate
Test: m BUILD_DATETIME=1234 shows up in ro.build.version.incremental
Change-Id: I8444beb2b47a49095ef760083fc85f220821bffe
1 file changed
tree: 9be218025925075dfe94490b9e8e4b12dd57e23b
  1. core/
  2. target/
  3. tests/
  4. tools/
  5. .gitignore
  6. Android.mk
  7. buildspec.mk.default
  8. Changes.md
  9. CleanSpec.mk
  10. envsetup.sh
  11. help.sh
  12. navbar.md
  13. OWNERS
  14. README.md
  15. tapasHelp.sh
  16. Usage.txt
README.md

Android Make Build System

This is the Makefile-based portion of the Android Build System.

For documentation on how to run a build, see Usage.txt

For a list of behavioral changes useful for Android.mk writers see Changes.md

For an outdated reference on Android.mk files, see build-system.html. Our Android.mk files look similar, but are entirely different from the Android.mk files used by the NDK build system. When searching for documentation elsewhere, ensure that it is for the platform build system -- most are not.

This Makefile-based system is in the process of being replaced with Soong, a new build system written in Go. During the transition, all of these makefiles are read by Kati, and generate a ninja file instead of being executed directly. That's combined with a ninja file read by Soong so that the build graph of the two systems can be combined and run as one.