build-script: reduce duplication of check

This hoists the shared check to the beginning of the product
installation phase.  This can be done as a shared phase option.  In
theory it should be possible to hoist this further to a single check at
the beginning of the phase.

Author: compnerd

utils/build-script-impl

@@ -2679,6 +2679,10 @@ for host in "${ALL_HOSTS[@]}"; do
         if ! [[ $(should_execute_action "${host}-${tmp_product}-install") ]]; then
             continue
         fi
+        if [[ -z "${INSTALL_DESTDIR}" ]] ; then
+            echo "--install-destdir is required to install products."
+            exit 1
+        fi
 
         INSTALL_TARGETS="install"
 
@@ -2721,20 +2725,12 @@ for host in "${ALL_HOSTS[@]}"; do
                 if [[ -z "${INSTALL_LLDB}" ]] ; then
                     continue
                 fi
-                if [[ -z "${INSTALL_DESTDIR}" ]] ; then
-                    echo "--install-destdir is required to install products."
-                    exit 1
-                fi
                 INSTALL_TARGETS="install-distribution"
                 ;;
             xctest)
                 if [[ -z "${INSTALL_XCTEST}" ]] ; then
                     continue
                 fi
-                if [[ -z "${INSTALL_DESTDIR}" ]] ; then
-                    echo "--install-destdir is required to install products."
-                    exit 1
-                fi
 
                 case ${host} in
                   linux-*|freebsd-*|cygwin-*|haiku-*|android-*) ;;
@@ -2756,11 +2752,6 @@ for host in "${ALL_HOSTS[@]}"; do
                     continue
                 fi
 
-                if [[ -z "${INSTALL_DESTDIR}" ]] ; then
-                    echo "--install-destdir is required to install products."
-                    exit 1
-                fi
-
                 ;;
             libdispatch|libdispatch_static)
                 if [[ -z "${INSTALL_LIBDISPATCH}" ]] ; then
@@ -2794,10 +2785,6 @@ for host in "${ALL_HOSTS[@]}"; do
                 if [[ -z "${INSTALL_LIBICU}" ]]; then
                     continue
                 fi
-                if [[ -z "${INSTALL_DESTDIR}" ]] ; then
-                    echo "--install-destdir is required to install products."
-                    exit 1
-                fi
                 echo "--- Installing ${product} ---"
                 ICU_BUILD_DIR=$(build_directory ${host} ${product})
                 ICU_INSTALL_DIR="$(get_host_install_destdir ${host})$(get_host_install_prefix ${host})"
@@ -2835,10 +2822,6 @@ for host in "${ALL_HOSTS[@]}"; do
                 if [[ -z "${INSTALL_PLAYGROUNDSUPPORT}" ]] ; then
                     continue
                 fi
-                if [[ -z "${INSTALL_DESTDIR}" ]] ; then
-                    echo "--install-destdir is required to install products."
-                    exit 1
-                fi
 
                 echo "--- Installing ${product} ---"
 
@@ -2874,11 +2857,6 @@ for host in "${ALL_HOSTS[@]}"; do
                 ;;
         esac
 
-        if [[ -z "${INSTALL_DESTDIR}" ]] ; then
-            echo "--install-destdir is required to install products."
-            exit 1
-        fi
-
         echo "--- Installing ${product} ---"
         build_dir=$(build_directory ${host} ${product})