TEMPLATE.sh: Die, if BUILD_TMPDIR can't be removed

If we don't have the permissions to remove BUILD_TMPDIR (which is quite
likely, when we switch from a test build with a personal user to one
via tools/build.sh with the build user), the current code would ignore
the fact, that the directory can't be removed and continue with a
nonempty directory, possible running into permission problems later.

We could just change

   chmod ... && rm -r ...

to

   ( chmod ... ; rm -r ... )

and the shell would terminate when chmod fails due to permissions.
However, the error message of chmod is different than that of rm:

    buczek@afk:~$ chmod u+w /root
    chmod: changing permissions of ‘/root’: Operation not permitted
    buczek@afk:~$ ls /root/
    ls: cannot open directory /root/: Permission denied

I think "Permission denied" is a bit clearer than "Operation not
permitted".

Ignore errors form `chmod` and try `rm` in any case, which either
succeeds or aborts the script with an appropriate error message. Remove
-c flag from chmod because we are not really interested if something has
been changed or not.

TEMPLATE.sh

@@ -11,7 +11,7 @@ set -xe
 umask 022
 
 BUILD_TMPDIR=/dev/shm/$PKG-$VERSION-$BUILD.build.tmp
-test -d $BUILD_TMPDIR && chmod -c -R u+rwx $BUILD_TMPDIR && rm -rf $BUILD_TMPDIR
+test -d $BUILD_TMPDIR && ( chmod -R u+rwx $BUILD_TMPDIR || true ; rm -rf $BUILD_TMPDIR )
 mkdir -p $BUILD_TMPDIR/home
 export TMPDIR=$BUILD_TMPDIR
 export HOME=$BUILD_TMPDIR/home