Add support for single-value product variables

Prior to this change, all PRODUCT_* variables are inherited with
list semantics, meaning the variable value in the current makefile
as well as all the makefiles it inherits are concatenated together.

Many of these variables are not lists, so this change adds the
ability to classify a variable as a single-value variable, which
will inherit at most one value (the first one), unless the variable
is already defined in the current file.

This change also marks all current variables as list variables.
A future change will re-classify the single-value variables as such.

Bug: 116769560
Test: presubmit
Change-Id: I57719a5eefd0749e92c08b1773b6f929629267a3
2 files changed
tree: 03e833b39fc5710a1b0ed4b73fac4f9fc5fe48f2
  1. common/
  2. core/
  3. packaging/
  4. target/
  5. tests/
  6. tools/
  7. .gitignore
  8. buildspec.mk.default
  9. Changes.md
  10. CleanSpec.mk
  11. Deprecation.md
  12. envsetup.sh
  13. help.sh
  14. navbar.md
  15. OWNERS
  16. README.md
  17. tapasHelp.sh
  18. 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For an outdated reference on Android.mk files, see build-system.html.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.