use MD5SUM env variable adn not md5sum directly

Change-Id: I985b3373edcd0bfc151adfa92b79a6b5080d22ad
Reviewed-on: https://gerrit.libreoffice.org/3805Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Tested-by: Norbert Thiebaud <nthiebaud@gmail.com>

solenv/bin/modules/installer.pm

@@ -464,7 +464,7 @@ sub run {
         if (length($loglanguagestring) > $installer::globals::max_lang_length)
         {
             my $number_of_languages = installer::systemactions::get_number_of_langs($loglanguagestring);
-            chomp(my $shorter = `echo $loglanguagestring | md5sum | sed -e "s/ .*//g"`);
+            chomp(my $shorter = `echo $loglanguagestring | $ENV{'MD5SUM'} | sed -e "s/ .*//g"`);
             my $id = substr($shorter, 0, 8); # taking only the first 8 digits
             $loglanguagestring = "lang_" . $number_of_languages . "_id_" . $id;
         }

solenv/bin/modules/installer/systemactions.pm

@@ -266,7 +266,7 @@ sub create_directories
                 if (length($languagestring) > $installer::globals::max_lang_length )
                 {
                     my $number_of_languages = get_number_of_langs($languagestring);
-                    chomp(my $shorter = `echo $languagestring | md5sum | sed -e "s/ .*//g"`);
+                    chomp(my $shorter = `echo $languagestring | $ENV{'MD5SUM'} | sed -e "s/ .*//g"`);
                     my $id = substr($shorter, 0, 8); # taking only the first 8 digits
                     $languagestring = "lang_" . $number_of_languages . "_id_" . $id;
                 }