Remove the --install parameter when running aclocal.  The --install
argument is used to copy third-party files to the first -I directory.
gnutls has -I m4 first, which would copy files to its local build
directory.  However, openwrt prepends the staging dir m4 directory,
causing aclocal --install to copy an old definition of
ax_code_coverage.m4 into the staging dir.

If strace is built after gnutls, compilation will fail:

    Makefile:9303: *** missing separator.  Stop.

The version of ax_code_coverage.m4 that gets installed does not define
@CODE_COVERAGE_RULES@.

Removing the --install parameter in gnutls solves the issue.

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>