run-tests: find current version of aapt in folder rather than in PATH

Not everyone adds the build-tools to their PATH, so this makes it so this
script will find aapt in the most recent build-tools version that is
installed on the local system.

tests/run-tests

@@ -12,7 +12,7 @@ copy_apks_into_repo() {
     set +x
     for f in `find $APKDIR -name '*.apk' | grep -F -v -e unaligned -e unsigned`; do
         name=$(basename $(dirname `dirname $f`))
-        apk=`aapt dump badging "$f" | sed -n "s,^package: name='\(.*\)' versionCode='\([0-9][0-9]*\)' .*,\1_\2.apk,p"`
+        apk=`$aapt dump badging "$f" | sed -n "s,^package: name='\(.*\)' versionCode='\([0-9][0-9]*\)' .*,\1_\2.apk,p"`
         test $f -nt repo/$apk && rm -f repo/$apk  # delete existing if $f is newer
         if [ ! -e repo/$apk ] && [ ! -e archive/$apk ]; then
             echo "$f --> repo/$apk"
@@ -47,6 +47,12 @@ if [ $# -ne 1 ]; then
     exit 1
 fi
 
+if [ -z $ANDROID_HOME ]; then
+    echo "ANDROID_HOME must be set with the path to the Android SDK, i.e.: "
+    echo "  export ANDROID_HOME=/opt/android-sdk"
+    exit 1
+fi
+
 APKDIR=$1
 
 if [ -z $WORKSPACE ]; then
@@ -59,6 +65,11 @@ if [ -z $fdroid ]; then
     fdroid="$WORKSPACE/fdroid"
 fi
 
+# allow the location of aapt to be overridden
+if [ -z $aapt ]; then
+    aapt=`ls -1 $ANDROID_HOME/build-tools/*/aapt | sort | tail -1`
+fi
+
 #------------------------------------------------------------------------------#
 echo_header "setup a new repo from scratch using ANDROID_HOME"