Fix issue where linux_bionic cannot find build number

For some reason linux_bionic builds don't seem to be able to find the
build-number unless we've lunched to something. Do that and fix up for
the new location of the build-number.txt file.

Bug: 151059142
Test: DIST_DIR=$PWD/out/dist ./art/tools/dist_linux_bionic.sh -j80 com.android.art.host com.android.support.apexer
Change-Id: If2ad57f4301d723b2a53f741643826682d5863b0
diff --git a/tools/build_linux_bionic.sh b/tools/build_linux_bionic.sh
index 70f871f..89e72b2 100755
--- a/tools/build_linux_bionic.sh
+++ b/tools/build_linux_bionic.sh
@@ -35,6 +35,8 @@
 # Soong needs a bunch of variables set and will not run if they are missing.
 # The default values of these variables is only contained in make, so use
 # nothing to create the variables then remove all the other artifacts.
+# Lunch since it seems we cannot find the build-number otherwise.
+lunch aosp_x86-eng
 build/soong/soong_ui.bash --make-mode nothing
 
 if [ $? != 0 ]; then
@@ -49,7 +51,7 @@
 # There is no good way to force soong to generate host-bionic builds currently
 # so this is a hacky workaround.
 tmp_soong_var=$(mktemp --tmpdir soong.variables.bak.XXXXXX)
-tmp_build_number=$(cat ${out_dir}/build_number.txt)
+tmp_build_number=$(cat ${out_dir}/soong/build_number.txt)
 
 cat $out_dir/soong/soong.variables > ${tmp_soong_var}
 
@@ -82,6 +84,6 @@
 rm $tmp_soong_var
 
 # Write a new build-number
-echo ${tmp_build_number}_SOONG_ONLY_BUILD > ${out_dir}/build_number.txt
+echo ${tmp_build_number}_SOONG_ONLY_BUILD > ${out_dir}/soong/build_number.txt
 
 build/soong/soong_ui.bash --make-mode --skip-make $@