STT: fix build error for the ninja explain argument

The command must be in quotations. Use eval to run commands.

Bug: 284915566
Test: combined_build_test.sh -t cf_x86_64_phone -v userdebug \
                   -d out/dist -a cf_x86_64_foldable -o -c droid
Change-Id: I41881527434a05736224de502ff6b09dcc45a55c

treble/combined_build_test.sh

@@ -86,7 +86,7 @@ fi
 run_command() {
     echo "Running: ${1}"
     if [[ -z "${dry_run}" ]]; then
-        $1
+        eval "${1}"
     fi
 }