Speed up lunch/tapas/etc. shell utility functions.

1. Combined ~10 calls to the make build system to only one.
   We added a phony target "dump-many-vars" to the build system to dump
   "<var>=<value>" pairs. We then store the pairs as shell variables.
   With this cache get_build_var/get_abs_build_var can just return
   the shell variables instead of querying the build system.
2. Prune .git when we search for AndroidProduct.mks.

In internal source tree lunch time was reduced from ~15s to ~1.5s.

Bug: 27429759
Change-Id: I24e88598f6fab598ef26518885fd5e86e71a772d
diff --git a/core/dumpvar.mk b/core/dumpvar.mk
index cfb031f..36fd08a 100644
--- a/core/dumpvar.mk
+++ b/core/dumpvar.mk
@@ -1,3 +1,35 @@
+
+# List of variables we want to print in the build banner.
+print_build_config_vars := \
+  PLATFORM_VERSION_CODENAME \
+  PLATFORM_VERSION \
+  TARGET_PRODUCT \
+  TARGET_BUILD_VARIANT \
+  TARGET_BUILD_TYPE \
+  TARGET_BUILD_APPS \
+  TARGET_ARCH \
+  TARGET_ARCH_VARIANT \
+  TARGET_CPU_VARIANT \
+  TARGET_2ND_ARCH \
+  TARGET_2ND_ARCH_VARIANT \
+  TARGET_2ND_CPU_VARIANT \
+  HOST_ARCH \
+  HOST_2ND_ARCH \
+  HOST_OS \
+  HOST_OS_EXTRA \
+  HOST_CROSS_OS \
+  HOST_CROSS_ARCH \
+  HOST_CROSS_2ND_ARCH \
+  HOST_BUILD_TYPE \
+  BUILD_ID \
+  OUT_DIR
+
+ifeq ($(TARGET_BUILD_PDK),true)
+print_build_config_vars += \
+  TARGET_BUILD_PDK \
+  PDK_FUSION_PLATFORM_ZIP
+endif
+
 # ---------------------------------------------------------------
 # the setpath shell function in envsetup.sh uses this to figure out
 # what to add to the path given the config we have chosen.
@@ -59,38 +91,37 @@
 PRINT_BUILD_CONFIG:=
 endif
 
-endif # CALLED_FROM_SETUP
-
-
-ifneq ($(PRINT_BUILD_CONFIG),)
-HOST_OS_EXTRA:=$(shell python -c "import platform; print(platform.platform())")
-$(info ============================================)
-$(info   PLATFORM_VERSION_CODENAME=$(PLATFORM_VERSION_CODENAME))
-$(info   PLATFORM_VERSION=$(PLATFORM_VERSION))
-$(info   TARGET_PRODUCT=$(TARGET_PRODUCT))
-$(info   TARGET_BUILD_VARIANT=$(TARGET_BUILD_VARIANT))
-$(info   TARGET_BUILD_TYPE=$(TARGET_BUILD_TYPE))
-$(info   TARGET_BUILD_APPS=$(TARGET_BUILD_APPS))
-$(info   TARGET_ARCH=$(TARGET_ARCH))
-$(info   TARGET_ARCH_VARIANT=$(TARGET_ARCH_VARIANT))
-$(info   TARGET_CPU_VARIANT=$(TARGET_CPU_VARIANT))
-$(info   TARGET_2ND_ARCH=$(TARGET_2ND_ARCH))
-$(info   TARGET_2ND_ARCH_VARIANT=$(TARGET_2ND_ARCH_VARIANT))
-$(info   TARGET_2ND_CPU_VARIANT=$(TARGET_2ND_CPU_VARIANT))
-$(info   HOST_ARCH=$(HOST_ARCH))
-$(info   HOST_2ND_ARCH=$(HOST_2ND_ARCH))
-$(info   HOST_OS=$(HOST_OS))
-$(info   HOST_OS_EXTRA=$(HOST_OS_EXTRA))
-$(info   HOST_CROSS_OS=$(HOST_CROSS_OS))
-$(info   HOST_CROSS_ARCH=$(HOST_CROSS_ARCH))
-$(info   HOST_CROSS_2ND_ARCH=$(HOST_CROSS_2ND_ARCH))
-$(info   HOST_BUILD_TYPE=$(HOST_BUILD_TYPE))
-$(info   BUILD_ID=$(BUILD_ID))
-$(info   OUT_DIR=$(OUT_DIR))
-ifeq ($(TARGET_BUILD_PDK),true)
-$(info   TARGET_BUILD_PDK=$(TARGET_BUILD_PDK))
-$(info   PDK_FUSION_PLATFORM_ZIP=$(PDK_FUSION_PLATFORM_ZIP))
+ifneq ($(filter report_config,$(DUMP_MANY_VARS)),)
+# Construct the shell commands that print the config banner.
+report_config_sh := echo '============================================';
+report_config_sh += $(foreach v,$(print_build_config_vars),echo '$v=$($(v))';)
+report_config_sh += echo '============================================';
 endif
 
+# Dump mulitple variables to "<var>=<value>" pairs, one per line.
+# The output may be executed as bash script.
+# Input variables:
+#   DUMP_MANY_VARS: the list of variable names.
+#   DUMP_VAR_PREFIX: an optional prefix of the variable name added to the output.
+#   DUMP_MANY_ABS_VARS: the list of abs variable names.
+#   DUMP_ABS_VAR_PREFIX: an optional prefix of the abs variable name added to the output.
+.PHONY: dump-many-vars
+dump-many-vars :
+	@$(foreach v, $(filter-out report_config, $(DUMP_MANY_VARS)),\
+	  echo "$(DUMP_VAR_PREFIX)$(v)='$($(v))'";)
+ifneq ($(filter report_config, $(DUMP_MANY_VARS)),)
+	@# Construct a special variable for report_config.
+	@# Escape \` to defer the execution of report_config_sh to preserve the line breaks.
+	@echo "$(DUMP_VAR_PREFIX)report_config=\`$(report_config_sh)\`"
+endif
+	@$(foreach v, $(sort $(DUMP_MANY_ABS_VARS)),\
+	  echo "$(DUMP_ABS_VAR_PREFIX)$(v)='$(PWD)/$($(v))'";)
+
+endif # CALLED_FROM_SETUP
+
+ifneq ($(PRINT_BUILD_CONFIG),)
+$(info ============================================)
+$(foreach v, $(print_build_config_vars),\
+  $(info $v=$($(v))))
 $(info ============================================)
 endif