Use printf instead of echo, just in case

...$PRODUCTNAME happens to be -n (which is notoriously problematic with various
versions of echo).

Change-Id: I09dfb562689138aa0135982725bf2c254ce06e59
Reviewed-on: https://gerrit.libreoffice.org/50104Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

configure.ac

@@ -168,7 +168,7 @@ if test "$enable_release_build" = "" -o "$enable_release_build" = "no"; then
 fi
 AC_MSG_RESULT([$PRODUCTNAME])
 AC_SUBST(PRODUCTNAME)
-PRODUCTNAME_WITHOUT_SPACES=$(echo "$PRODUCTNAME" | sed 's/ //g')
+PRODUCTNAME_WITHOUT_SPACES=$(printf %s "$PRODUCTNAME" | sed 's/ //g')
 AC_SUBST(PRODUCTNAME_WITHOUT_SPACES)
 
 dnl ===================================================================