Run ckati step of the Android build tracing given variables

Test: `m nothing && build/soong/scripts/run-ckati.sh FOO BAR`, see FOO
and BAR assignments in out/ckati.trace

Change-Id: Ife8bb6d716bfde5ee9f75b85b1e5738ab2238dce

scripts/run-ckati.sh

@@ -0,0 +1,91 @@
+#! /bin/bash -eu
+
+# Run CKati step separately, tracing given Makefile variables.
+# It is expected that the regular Android null build (`m nothing`)
+# has been run so that $OUT_DIR/soong/Android-${TARGET_PRODUCT}.mk,
+# $OUT_DIR/soong/make_vars-${TARGET_PRODUCT}.mk, etc. files exist.
+#
+# The output file is in JSON format and can be processed with, say,
+# `jq`. For instance, the following invocation outputs all assignment
+# traces concisely:
+#  jq -c  '.assignments[] | (select (.operation == "assign")) | {("n"): .name, ("l"): .value_stack[0]?, ("v"): .value }' out/ckati.trace
+# generates
+#  {"n":"<var1>","l":"<file>:<line>","v":"<value1>"}
+#  ...
+
+function die() { format=$1; shift; printf "$format\n" $@; exit 1; }
+function usage() { die "Usage: %s [-o FILE] VAR ...\n(without -o the output goes to ${outfile})"  ${0##*/}; }
+
+[[ -d build/soong ]] || die "run this script from the top of the Android source tree"
+declare -r out=${OUT_DIR:-out}
+[[ -x ${out}/soong_ui ]] || die "run Android build first"
+: ${TARGET_PRODUCT:?not set, run lunch?}
+: ${TARGET_BUILD_VARIANT:?not set, run lunch?}
+declare -r androidmk=${out}/soong/Android-${TARGET_PRODUCT}.mk
+declare -r makevarsmk=${out}/soong/make_vars-${TARGET_PRODUCT}.mk
+declare -r target_device_dir=$(${out}/soong_ui --dumpvar-mode TARGET_DEVICE_DIR)
+: ${target_device_dir:?cannot find device directory for ${TARGET_PRODUCT}}
+declare -r target_device=$(${out}/soong_ui --dumpvar-mode TARGET_DEVICE)
+: ${target_device:?cannot find target device for ${TARGET_PRODUCT}}
+declare -r timestamp_file=${out}/build_date.txt
+# Files should exist, so ls should succeed:
+ls -1d "$androidmk" "$makevarsmk" "$target_device_dir" "$timestamp_file" >/dev/null
+
+outfile=${out}/ckati.trace
+while getopts "ho:" opt; do
+  case $opt in
+    h) usage ;;
+    o) outfile=$OPTARG ;;
+    ?) usage ;;
+  esac
+done
+
+if (($#>0)); then
+  declare -a tracing=(--variable_assignment_trace_filter="$*" --dump_variable_assignment_trace "$outfile")
+else
+  printf "running ckati without tracing variables\n"
+fi
+
+# Touch one input for ckati, otherwise it will just print
+# 'No need to regenerate ninja file' and exit.
+touch "$androidmk"
+prebuilts/build-tools/linux-x86/bin/ckati \
+  --gen_all_targets \
+  -i \
+  --ignore_optional_include=out/%.P \
+  --ninja \
+  --ninja_dir=out \
+  --ninja_suffix=-${TARGET_PRODUCT} \
+  --no_builtin_rules \
+  --no_ninja_prelude \
+  --regen \
+  --top_level_phony \
+  --use_find_emulator \
+  --use_ninja_phony_output \
+  --use_ninja_symlink_outputs \
+  --werror_find_emulator \
+  --werror_implicit_rules \
+  --werror_overriding_commands \
+  --werror_phony_looks_real \
+  --werror_real_to_phony \
+  --werror_suffix_rules \
+  --werror_writable \
+  --writable out/ \
+  -f build/make/core/main.mk \
+  "${tracing[@]}" \
+  ANDROID_JAVA_HOME=prebuilts/jdk/jdk17/linux-x86 \
+  ASAN_SYMBOLIZER_PATH=$PWD/prebuilts/clang/host/linux-x86/llvm-binutils-stable/llvm-symbolizer \
+  BUILD_DATETIME_FILE="$timestamp_file" \
+  BUILD_HOSTNAME=$(hostname) \
+  BUILD_USERNAME="$USER" \
+  JAVA_HOME=$PWD/prebuilts/jdk/jdk17/linux-x86 \
+  KATI_PACKAGE_MK_DIR="{$out}/target/product/${target_device}/CONFIG/kati_packaging" \
+  OUT_DIR="$out" \
+  PATH="$PWD/prebuilts/build-tools/path/linux-x86:$PWD/${out}/.path" \
+  PYTHONDONTWRITEBYTECODE=1 \
+  SOONG_ANDROID_MK="$androidmk" \
+  SOONG_MAKEVARS_MK="$makevarsmk" \
+  TARGET_BUILD_VARIANT="$TARGET_BUILD_VARIANT" \
+  TARGET_DEVICE_DIR="$target_device_dir" \
+  TARGET_PRODUCT=${TARGET_PRODUCT} \
+  TMPDIR="$PWD/$out/soong/.temp"