Fix zts support on self-hosted envs

Author: shivammathur

src/scripts/linux.sh

@@ -185,7 +185,7 @@ update_php() {
 
 # Function to install PHP.
 add_php() {
-  if [ "${runner:?}" = "self-hosted" ] || [ "${use_package_cache:-true}" = "false" ]; then
+  if [[ "$ts" != "zts" && ("${runner:?}" = "self-hosted" ||  "${use_package_cache:-true}" = "false") ]]; then
     if [[ "$version" =~ ${nightly_versions:?} ]]; then
         setup_nightly
     else