Enhance %make_build replacement

[marxin]

Thank you Tom for #229. However, looking at the all SPEC files I see that V=1 and VERBOSE=1 can be stripped right now:

$ grep 'make.*smp_mflags.*VERBOSE=1' * | wc -l
82
$ grep 'make.*smp_mflags.*VERBOSE=1' * | head
allegro.spec:make %{?_smp_mflags} VERBOSE=1
automake.spec:make %{?_smp_mflags} check VERBOSE=1
automake-testsuite.spec:make %{?_smp_mflags} check VERBOSE=1
bcc.spec:make %{?_smp_mflags} VERBOSE=1
bcc.spec:make %{?_smp_mflags} VERBOSE=1
bemenu.spec:make %{?_smp_mflags} VERBOSE=1
boomaga.spec:make %{?_smp_mflags} VERBOSE=1
CharLS.spec:make %{?_smp_mflags} VERBOSE=1
clucene-core.spec:make %{?_smp_mflags} VERBOSE=1
converseen.spec:make %{?_smp_mflags} VERBOSE=1
$ grep 'make.*V=1.*smp_mflags' * | wc -l
61
$ grep 'make.*V=1.*smp_mflags' * | head
adios.spec:make V=1 %{?_smp_mflags}
alsa.spec:make V=1 %{?_smp_mflags}
beaver.spec:make V=1 %{?_smp_mflags} all doc
btrfsprogs.spec:make V=1 %{?_smp_mflags} all \
cgit.spec:make V=1 prefix="%_prefix" CFLAGS="%optflags" %{?_smp_mflags} all
clamav.spec:make V=1 %?_smp_mflags
cogl.spec:make V=1 # %{?_smp_mflags} disabled, as it randomly fails for now
criu.spec:make V=1 %{?_smp_mflags} %{?make_options}
dpdk.spec:make V=1 O=%{target} T=%{target} %{?_smp_mflags} config
dpdk.spec:	make V=1 O=%{target}-$flavor T=%{target} %{?_smp_mflags} config
$ grep 'make.*smp_mflags.*V=1' * | wc -l
452
$ grep 'make.*smp_mflags.*V=1' * | head
acl.spec:make %{?_smp_mflags} V=1
anjuta.spec:make %{?_smp_mflags} V=1
apulse.spec:make %{?_smp_mflags} V=1
arc-gtk-theme.spec:make %{?_smp_mflags} V=1
atril.spec:make %{?_smp_mflags} V=1
audacious-plugins.spec:make %{?_smp_mflags} V=1
audacious.spec:make %{?_smp_mflags} V=1
awesome.spec:make %{?_smp_mflags} V=1
ayatana-ido.spec:make %{?_smp_mflags} V=1
babeltrace.spec:make %{?_smp_mflags} V=1