faster to compile.

A small selection of packages was tested going from:

Executed in  696.30 secs   fish           external
   usr time   82.98 mins  395.00 micros   82.98 mins
   sys time    9.02 mins    0.00 micros    9.02 mins

to:

Executed in  592.20 secs   fish           external
   usr time   84.84 mins  361.00 micros   84.84 mins
   sys time    8.85 mins   57.00 micros    8.85 mins

Tested by running make -j 12 and wiping staging/build_dir/target_x

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Added miscellaneous fixes.

Fixed PKG_NAME to a sane one as v$(PKG_VERSION) can conflict with
others.

Separate CMAKE_OPTIONS in lines for clarity.

Add JUST_INSTALL_CEREAL to fix compilation with mips64.

Signed-off-by: Rosen Penev <rosenp@gmail.com>

Signed-off-by: David Woodhouse <dwmw2@infradead.org>