Introduce per-product per-module dex-preopt config

- Added LOCAL_DEX_PREOPT_FLAGS to pass extra flags to dex2oat.
- Added macro add-product-dex-preopt-module-config to specify almost
  arbitrary dex-preopt config/flags to modules in product
  configuration:
  $(call \
  add-product-dex-preopt-module-config,<module_name_list>,<config_or_flags>)
  How <config_or_flags> is interpreted is decided by
  dex_preopt_odex_install.mk and dex2oat. For now if it's "disable" we
  disable dexpreopt for the given modules; otherwise pass it to dex2oat as
  command line flags.
- If there are multiple configs for the same module in the product
  inheritance, the first takes precedence.
- Added PRODUCT_DEX_PREOPT_DEFAULT_FLAGS so you can specify default
  dex2oat flags in product configuration.
- Added PRODUCT_DEX_PREOPT_BOOT_FLAGS to specify flags of building boot.oat.

Bug: 17791867
(cherry picked from commit 20ebd2ef081f2a3e85a4adcf8837e6f5b68bdeea)

Change-Id: I2ee36892b40655c96837ee7a663dda1d25830878
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index f23c4a6..92b3fc4 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -123,6 +123,7 @@
 LOCAL_RENDERSCRIPT_TARGET_API:=
 LOCAL_DEX_PREOPT:= # '',true,false,nostripping
 LOCAL_DEX_PREOPT_IMAGE_LOCATION:=
+LOCAL_DEX_PREOPT_FLAGS:=
 LOCAL_PROTOC_OPTIMIZE_TYPE:= # lite(default),micro,nano,full
 LOCAL_PROTOC_FLAGS:=
 LOCAL_PROTO_JAVA_OUTPUT_PARAMS:=