More performance improvements

Instead of using `x := $(x) foo`, make sure `x` is initialized first,
then use `x += foo`.

For a aosp-master/aosp_crosshatch-userdebug build, this takes the build
from 49s to 33s (no significant difference in peak memory)

Bug: 158488548
Test: build-aosp_crosshatch.ninja is the same before/after
Change-Id: I41fb7611030dd3ba824f896a9c9eadbdd218f464

core/binary.mk

@@ -1799,7 +1799,7 @@ export_include_deps += $(strip \
      $(call intermediates-dir-for,HEADER_LIBRARIES,$(l),$(my_kind),,$(LOCAL_2ND_ARCH_VAR_PREFIX),$(my_host_cross))))
 
 ifneq ($(strip $(my_export_c_include_dirs)$(export_include_deps)),)
-  EXPORTS_LIST := $(EXPORTS_LIST) $(intermediates)
+  EXPORTS_LIST += $(intermediates)
   EXPORTS.$(intermediates).FLAGS := $(foreach d,$(my_export_c_include_dirs),-I $(call clean-path,$(d)))
   EXPORTS.$(intermediates).REEXPORT := $(export_include_deps)
   EXPORTS.$(intermediates).DEPS := $(my_export_c_include_deps) $(my_generated_sources) $(LOCAL_EXPORT_C_INCLUDE_DEPS)

core/cc_prebuilt_internal.mk

@@ -75,7 +75,7 @@ else  # my_strip_module not true
   built_module := $(LOCAL_BUILT_MODULE)
 
 ifdef prebuilt_module_is_a_library
-EXPORTS_LIST := $(EXPORTS_LIST) $(intermediates)
+EXPORTS_LIST += $(intermediates)
 EXPORTS.$(intermediates).FLAGS := $(foreach d,$(LOCAL_EXPORT_C_INCLUDE_DIRS),-I $(d))
 EXPORTS.$(intermediates).DEPS := $(LOCAL_EXPORT_C_INCLUDE_DEPS)
 

core/definitions.mk

@@ -110,6 +110,15 @@ ALL_DISABLED_PRESUBMIT_TESTS :=
 # All compatibility suites mentioned in LOCAL_COMPATIBILITY_SUITES
 ALL_COMPATIBILITY_SUITES :=
 
+# All LINK_TYPE entries
+ALL_LINK_TYPES :=
+
+# All exported/imported include entries
+EXPORTS_LIST :=
+
+# All modules already converted to Soong
+SOONG_ALREADY_CONV :=
+
 ###########################################################
 ## Debugging; prints a variable list to stdout
 ###########################################################

core/link_type.mk

@@ -12,7 +12,7 @@
 
 my_link_prefix := LINK_TYPE:$(call find-idf-prefix,$(my_kind),$(my_host_cross)):$(if $(my_common),$(my_common):_,_:$(if $(my_2nd_arch_prefix),$(my_2nd_arch_prefix),_))
 link_type := $(my_link_prefix):$(LOCAL_MODULE_CLASS):$(LOCAL_MODULE)
-ALL_LINK_TYPES := $(ALL_LINK_TYPES) $(link_type)
+ALL_LINK_TYPES += $(link_type)
 $(link_type).TYPE := $(my_link_type)
 $(link_type).MAKEFILE := $(LOCAL_MODULE_MAKEFILE)
 $(link_type).WARN := $(my_warn_types)

core/soong_android_app_set.mk

@@ -31,4 +31,4 @@ LOCAL_POST_INSTALL_CMD := unzip -qo -j -d $(dir $(LOCAL_INSTALLED_MODULE)) \
 $(LOCAL_INSTALLED_MODULE): PRIVATE_POST_INSTALL_CMD := $(LOCAL_POST_INSTALL_CMD)
 PACKAGES.$(LOCAL_MODULE).OVERRIDES := $(strip $(LOCAL_OVERRIDES_PACKAGES))
 
-SOONG_ALREADY_CONV := $(SOONG_ALREADY_CONV) $(LOCAL_MODULE)
+SOONG_ALREADY_CONV += $(LOCAL_MODULE)

core/soong_app_prebuilt.mk

@@ -218,4 +218,4 @@ ifdef LOCAL_PREBUILT_COVERAGE_ARCHIVE
   $(LOCAL_INSTALLED_MODULE): $(my_coverage_files)
 endif
 
-SOONG_ALREADY_CONV := $(SOONG_ALREADY_CONV) $(LOCAL_MODULE)
+SOONG_ALREADY_CONV += $(LOCAL_MODULE)

core/soong_cc_prebuilt.mk

@@ -51,7 +51,7 @@ include $(BUILD_SYSTEM)/base_rules.mk
 
 ifneq ($(filter STATIC_LIBRARIES SHARED_LIBRARIES HEADER_LIBRARIES,$(LOCAL_MODULE_CLASS)),)
   # Soong module is a static or shared library
-  EXPORTS_LIST := $(EXPORTS_LIST) $(intermediates)
+  EXPORTS_LIST += $(intermediates)
   EXPORTS.$(intermediates).FLAGS := $(LOCAL_EXPORT_CFLAGS)
   EXPORTS.$(intermediates).DEPS := $(LOCAL_EXPORT_C_INCLUDE_DEPS)
 
@@ -61,7 +61,7 @@ ifneq ($(filter STATIC_LIBRARIES SHARED_LIBRARIES HEADER_LIBRARIES,$(LOCAL_MODUL
     $(my_all_targets): $(LOCAL_BUILT_MODULE).toc
   endif
 
-  SOONG_ALREADY_CONV := $(SOONG_ALREADY_CONV) $(LOCAL_MODULE)
+  SOONG_ALREADY_CONV += $(LOCAL_MODULE)
 
   my_link_type := $(LOCAL_SOONG_LINK_TYPE)
   my_warn_types :=

core/soong_java_prebuilt.mk

@@ -173,4 +173,4 @@ $(my_exported_sdk_libs_file):
 		$(hide) echo $(PRIVATE_EXPORTED_SDK_LIBS) | tr ' ' '\n' > $@,\
 		$(hide) touch $@)
 
-SOONG_ALREADY_CONV := $(SOONG_ALREADY_CONV) $(LOCAL_MODULE)
+SOONG_ALREADY_CONV += $(LOCAL_MODULE)