Add script for building all target arch's needed in AML (Android Mainline)

prebuilts.

This runs Soong in skip-make mode, using normal in-make mode only to query
platform versions.

The same ${OUT_DIR} cannot be used for both skip-make and in-make builds,
because Soong generates a smaller build.ninja file in in-make builds where
many build targets are expected to be provided by the mk files. Thus this
script avoids using ${OUT_DIR} if it's an in-make build, defaulting instead
to out-aml/.

The script is based on build-ndk-prebuilts.sh, but uses a separate Soong
variable Aml_abis to enable the appropriate target architectures for
Mainline modules. Aml_abis is very similar to Ndk_abis, except "armeabi-v7a"
is used instead of "armeabi", which is necessary to match prebuilt
dependencies, e.g. for LLVM.

Test: build/soong/scripts/build-aml-prebuilts.sh libart libdexfile_external
  (verify that libraries for arm, arm64, x86, x86_64 are built)
Test: build/soong/scripts/build-aml-prebuilts.sh \
  out-aml/soong/.intermediates/external/conscrypt/conscrypt-module-sdk/android_common/conscrypt-module-sdk-current.zip
  (verify that the zip file contains libconscrypt_jni.so's for all four arches)
Test: build/soong/scripts/build-aml-prebuilts.sh com.android.art.{release,debug,testing,host}
  (verify that the build completes)
Test: Two identical build/soong/scripts/build-aml-prebuilts.sh runs after each other
  (verify that the 2nd run completes both Soong and ninja steps quickly without any building)
Change-Id: I35712f9f8f0b1cbb77107314c5927c6720e6c3bf

scripts/build-aml-prebuilts.sh

@@ -0,0 +1,75 @@
+#!/bin/bash -e
+
+export OUT_DIR=${OUT_DIR:-out}
+
+if [ -e ${OUT_DIR}/soong/.soong.in_make ]; then
+  # If ${OUT_DIR} has been created without --skip-make, Soong will create an
+  # ${OUT_DIR}/soong/build.ninja that leaves out many targets which are
+  # expected to be supplied by the .mk files, and that might cause errors in
+  # "m --skip-make" below. We therefore default to a different out dir
+  # location in that case.
+  AML_OUT_DIR=out-aml
+  echo "Avoiding in-make OUT_DIR '${OUT_DIR}' - building in '${AML_OUT_DIR}' instead"
+  OUT_DIR=${AML_OUT_DIR}
+fi
+
+source build/envsetup.sh
+
+my_get_build_var() {
+  # get_build_var will run Soong in normal in-make mode where it creates
+  # .soong.in_make. That would clobber our real out directory, so we need to
+  # run it in a different one.
+  OUT_DIR=${OUT_DIR}/get_build_var get_build_var "$@"
+}
+
+PLATFORM_SDK_VERSION=$(my_get_build_var PLATFORM_SDK_VERSION)
+PLATFORM_VERSION=$(my_get_build_var PLATFORM_VERSION)
+PLATFORM_VERSION_ALL_CODENAMES=$(my_get_build_var PLATFORM_VERSION_ALL_CODENAMES)
+
+# PLATFORM_VERSION_ALL_CODENAMES is a comma separated list like O,P. We need to
+# turn this into ["O","P"].
+PLATFORM_VERSION_ALL_CODENAMES=${PLATFORM_VERSION_ALL_CODENAMES/,/'","'}
+PLATFORM_VERSION_ALL_CODENAMES="[\"${PLATFORM_VERSION_ALL_CODENAMES}\"]"
+
+# Logic from build/make/core/goma.mk
+if [ "${USE_GOMA}" = true ]; then
+  if [ -n "${GOMA_DIR}" ]; then
+    goma_dir="${GOMA_DIR}"
+  else
+    goma_dir="${HOME}/goma"
+  fi
+  GOMA_CC="${goma_dir}/gomacc"
+  export CC_WRAPPER="${CC_WRAPPER}${CC_WRAPPER:+ }${GOMA_CC}"
+  export CXX_WRAPPER="${CXX_WRAPPER}${CXX_WRAPPER:+ }${GOMA_CC}"
+  export JAVAC_WRAPPER="${JAVAC_WRAPPER}${JAVAC_WRAPPER:+ }${GOMA_CC}"
+else
+  USE_GOMA=false
+fi
+
+SOONG_OUT=${OUT_DIR}/soong
+mkdir -p ${SOONG_OUT}
+SOONG_VARS=${SOONG_OUT}/soong.variables
+
+cat > ${SOONG_VARS}.new << EOF
+{
+    "Platform_sdk_version": ${PLATFORM_SDK_VERSION},
+    "Platform_sdk_codename": "${PLATFORM_VERSION}",
+    "Platform_version_active_codenames": ${PLATFORM_VERSION_ALL_CODENAMES},
+
+    "DeviceName": "generic_arm64",
+    "HostArch": "x86_64",
+    "Aml_abis": true,
+
+    "UseGoma": ${USE_GOMA}
+}
+EOF
+
+if [ -f ${SOONG_VARS} ] && cmp -s ${SOONG_VARS} ${SOONG_VARS}.new; then
+  # Don't touch soong.variables if we don't have to, to avoid Soong rebuilding
+  # the ninja file when it isn't necessary.
+  rm ${SOONG_VARS}.new
+else
+  mv ${SOONG_VARS}.new ${SOONG_VARS}
+fi
+
+m --skip-make "$@"