Handle symlinked OUT_DIRs (again)

My previous attempt at properly handling symlinked OUT_DIRs only worked
if the symlink was to a different directory, not one in the same
directory.

This time, make sure that both make and soong use the same
representation of the output directory by passing BUILDDIR to
bootstrap.bash. Soong has been updated to pick whether to use a relative
or absolute path back to the source tree depending on what makes sense.
If the BUILDDIR or the path back to the source tree change, re-run the
bootstrap.

Also, move the $OUT_DIR/Android.mk and $OUT_DIR/CleanSpec.mk generation
to before Kati runs. In the case that $TOP/out was symlinked to
$TOP/out.angler:

 1) Soong generates out.angler/soong/Android.mk
 2) Kati's find generator produces in-memory tree of the filesystem
 3) $(shell ) creates out.angler/Android.mk
 4) The emulated findleaves Android.mk search finds
    out.angler/soong/Android.mk since the in-memory tree is never updated.

This doesn't happen in the normal case, because we pass --prune=$OUT_DIR
to findleaves.

Change-Id: Ib0fdae2e80f75ddcf33a3c8c5ea0978f5308b437
(cherry picked from commit cc60f01357)
[ccross: resolved conflicts in nyc-dev]

core/main.mk

@@ -116,11 +116,6 @@ ifndef BUILDING_WITH_NINJA
 $(shell rm -f $(OUT_DIR)/ninja_build)
 endif
 
-# With these files findleaves.py won't be unnecessarily slower even if
-# there is a user creates a copy of $(OUT_DIR).
-$(shell echo '# This file prevents findleaves.py from traversing this directory further' > $(OUT_DIR)/Android.mk)
-$(shell echo '# This file prevents findleaves.py from traversing this directory further' > $(OUT_DIR)/CleanSpec.mk)
-
 # Write the build number to a file so it can be read back in
 # without changing the command line every time.  Avoids rebuilds
 # when using ninja.

core/ninja.mk

@@ -147,11 +147,18 @@ ninja_wrapper: $(COMBINED_BUILD_NINJA) $(MAKEPARALLEL)
 	@echo Starting build with ninja
 	+$(hide) export NINJA_STATUS="$(NINJA_STATUS)" && source $(KATI_ENV_SH) && $(NINJA_MAKEPARALLEL) $(NINJA) $(NINJA_GOALS) -C $(TOP) -f $(COMBINED_BUILD_NINJA) $(NINJA_ARGS)
 
+# Dummy Android.mk and CleanSpec.mk files so that kati won't recurse into the
+# out directory
+DUMMY_OUT_MKS := $(OUT_DIR)/Android.mk $(OUT_DIR)/CleanSpec.mk
+$(DUMMY_OUT_MKS):
+	@mkdir -p $(dir $@)
+	$(hide) echo '# This file prevents findleaves.py from traversing this directory further' >$@
+
 KATI_FIND_EMULATOR := --use_find_emulator
 ifeq ($(KATI_EMULATE_FIND),false)
   KATI_FIND_EMULATOR :=
 endif
-$(KATI_BUILD_NINJA): $(KATI) $(MAKEPARALLEL) $(SOONG_ANDROID_MK) FORCE
+$(KATI_BUILD_NINJA): $(KATI) $(MAKEPARALLEL) $(DUMMY_OUT_MKS) $(SOONG_ANDROID_MK) FORCE
 	@echo Running kati to generate build$(KATI_NINJA_SUFFIX).ninja...
 	+$(hide) $(KATI_MAKEPARALLEL) $(KATI) --ninja --ninja_dir=$(OUT_DIR) --ninja_suffix=$(KATI_NINJA_SUFFIX) --regen --ignore_dirty=$(OUT_DIR)/% --no_ignore_dirty=$(SOONG_ANDROID_MK) --ignore_optional_include=$(OUT_DIR)/%.P --detect_android_echo $(KATI_FIND_EMULATOR) -f build/core/main.mk $(KATI_GOALS) --gen_all_targets BUILDING_WITH_NINJA=true SOONG_ANDROID_MK=$(SOONG_ANDROID_MK)
 

core/soong.mk

@@ -3,30 +3,31 @@ SOONG_HOST_EXECUTABLES := $(SOONG_OUT_DIR)/host/$(HOST_PREBUILT_TAG)/bin
 KATI := $(SOONG_HOST_EXECUTABLES)/ckati
 MAKEPARALLEL := $(SOONG_HOST_EXECUTABLES)/makeparallel
 
-# This needs to exist before the realpath checks below
-$(shell mkdir -p $(SOONG_OUT_DIR))
-
-ifeq (,$(filter /%,$(SOONG_OUT_DIR)))
-SOONG_TOP_RELPATH := $(shell python -c "import os; print os.path.relpath('$(TOP)', '$(SOONG_OUT_DIR)')")
-# Protect against out being a symlink and relative paths not working
-ifneq ($(realpath $(SOONG_OUT_DIR)/$(SOONG_TOP_RELPATH)),$(realpath $(TOP)))
-SOONG_OUT_DIR := $(abspath $(SOONG_OUT_DIR))
-SOONG_TOP_RELPATH := $(abspath $(TOP))
-endif
-else
-SOONG_TOP_RELPATH := $(abspath $(TOP))
-endif
-
 SOONG := $(SOONG_OUT_DIR)/soong
+SOONG_BOOTSTRAP := $(SOONG_OUT_DIR)/.soong.bootstrap
 SOONG_BUILD_NINJA := $(SOONG_OUT_DIR)/build.ninja
 SOONG_ANDROID_MK := $(SOONG_OUT_DIR)/Android.mk
-SOONG_VARIABLES := $(SOONG_OUT_DIR)/soong.variables
 SOONG_IN_MAKE := $(SOONG_OUT_DIR)/.soong.in_make
+SOONG_VARIABLES := $(SOONG_OUT_DIR)/soong.variables
 
-# Bootstrap soong.  Run only the first time for clean builds
-$(SOONG):
+# We need to rebootstrap soong if SOONG_OUT_DIR or the reverse path from
+# SOONG_OUT_DIR to TOP changes
+SOONG_NEEDS_REBOOTSTRAP :=
+ifneq ($(wildcard $(SOONG_BOOTSTRAP)),)
+  ifneq ($(SOONG_OUT_DIR),$(strip $(shell source $(SOONG_BOOTSTRAP); echo $$BUILDDIR)))
+    SOONG_NEEDS_REBOOTSTRAP := FORCE
+    $(warning soong_out_dir changed)
+  endif
+  ifneq ($(strip $(shell build/soong/reverse_path.py $(SOONG_OUT_DIR))),$(strip $(shell source $(SOONG_BOOTSTRAP); echo $$SRCDIR_FROM_BUILDDIR)))
+    SOONG_NEEDS_REBOOTSTRAP := FORCE
+    $(warning reverse path changed)
+  endif
+endif
+
+# Bootstrap soong.
+$(SOONG_BOOTSTRAP): bootstrap.bash $(SOONG_NEEDS_REBOOTSTRAP)
 	$(hide) mkdir -p $(dir $@)
-	$(hide) cd $(dir $@) && $(SOONG_TOP_RELPATH)/bootstrap.bash
+	$(hide) BUILDDIR=$(SOONG_OUT_DIR) ./bootstrap.bash
 
 # Create soong.variables with copies of makefile settings.  Runs every build,
 # but only updates soong.variables if it changes
@@ -72,7 +73,7 @@ $(SOONG_IN_MAKE):
 	$(hide) touch $@
 
 # Build an Android.mk listing all soong outputs as prebuilts
-$(SOONG_ANDROID_MK): $(SOONG) $(SOONG_VARIABLES) $(SOONG_IN_MAKE) FORCE
+$(SOONG_ANDROID_MK): $(SOONG_BOOTSTRAP) $(SOONG_VARIABLES) $(SOONG_IN_MAKE) FORCE
 	$(hide) $(SOONG) $(KATI) $(MAKEPARALLEL) $(NINJA_ARGS)
 
 $(KATI): $(SOONG_ANDROID_MK)