Fix manifest generator args for arm64 DFU

The FLAGS prefix was previously omitted, which causes the
args to not be passed correctly. Thus the manifest that
was generated was mostly empty.

BUG: 143650197
Test: local run and manual inspection
Change-Id: I26ed481a2e59eff69837d2b194ada6a80c5ff728
diff --git a/tools/make_manifest.sh b/tools/make_manifest.sh
index a66c1e6..5ca03d8 100755
--- a/tools/make_manifest.sh
+++ b/tools/make_manifest.sh
@@ -57,7 +57,7 @@
 if [ ! -e manifest.txt ]; then
 	cat > manifest.txt << EOF
 ManifestVersion=1
-TftpServer=${tftp}
+TftpServer=${FLAGS_tftp}
 EOF
 fi
 }
@@ -84,16 +84,16 @@
 
 	if [ "${path}" != "" ]; then
 		filename=$(basename $path)
-
-		if [ $key == "UbootEnv" ] && [ ${file: -3} == ".gz" ]; then
+		filetype=`file -b --mime-type "${path}"`
+		if [ "$key" == "UbootEnv" ] && [ "${filetype}" == "application/gzip" ]; then
 			echo "error: gzip not supported for env images"
 		fi
-		if [ $key != "UbootEnv" ] && [ ${file: -3} != ".gz" ]; then
+		if [ "$key" != "UbootEnv" ] && [ "${filetype}" != "application/gzip" ]; then
 			echo "warning: gzip recommended for all non-env images"
 			confirm || exit 1
 		fi
-		if [ ! "${path}" -ef "${tftpdir}/${filename}" ]; then
-			cp "${path}" "${tftpdir}/"
+		if [ ! "${path}" -ef "${FLAGS_tftpdir}/${filename}" ]; then
+			cp "${path}" "${FLAGS_tftpdir}/"
 		fi
 	else
 		unset filename
@@ -104,8 +104,8 @@
 }
 
 createManifest
-addToManifest RootfsImg ${rootfs}
-addToManifest UbootEnv ${env}
-addToManifest TplSplImg ${loader1}
-addToManifest UbootItb ${loader2}
+addToManifest RootfsImg ${FLAGS_rootfs}
+addToManifest UbootEnv ${FLAGS_env}
+addToManifest TplSplImg ${FLAGS_loader1}
+addToManifest UbootItb ${FLAGS_loader2}
 makeSHA