Change config option for freetype2 in case if debian buster and above.

mod_php_install.sh

@@ -1271,7 +1271,6 @@ config_params="
    --with-curl \
    --enable-dba \
    --with-xpm-dir \
-   --with-freetype-dir \
    --enable-ftp \
    --with-gmp \
    --with-readline \
@@ -1301,6 +1300,20 @@ config_params="
 
 # --with-t1lib \
 
+# Note:
+#    Debian buster's package libfreetype6-dev is missing 'freetype-config'.
+#    but you can use pkg-config instead.
+#    Use '-enable-freetype', which relies on pkg-config instead of
+#    '--with-freetype-dir_DIR', which relies on freetype-config.
+#
+if [[ "$os_dist" = "debian" ]] && [[ $os_version -lt 10 ]] ; then
+   config_params="$config_params \
+   --with-freetype-dir"
+else
+   config_params="$config_params \
+   --enable-freetype"
+fi
+
 # --with-fpm-systemd \
 if $SYSTEMD_EXISTS ; then
     config_params="$config_params \