[build] Do not repeat autogen & configure every time

When doing code tweaking and manual builds with mb script, unconditionally
running autogen and configure leads to unnecessary full rebuilds every time.

Skip autogen and configure steps if they have already been done (based on
the existence of Makefile).

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>

rpm/usb-moded.spec

@@ -321,8 +321,8 @@ when the UI fails.
 %setup -q
 
 %build
-%autogen
-%configure --enable-app-sync --enable-meegodevlock --enable-debug --enable-connman --enable-systemd --enable-mer-ssu
+test -e Makefile || (%autogen)
+test -e Makefile || (%configure --enable-app-sync --enable-meegodevlock --enable-debug --enable-connman --enable-systemd --enable-mer-ssu)
 make all doc %{?_smp_mflags}
 
 %install