fix makepkg failing to find install, changelog

parent breaks building packages with install script and/or
changelog file.  these files "should reside in the same directory
as the PKGBUILD" according to PKGBUILD(5), but makepkg code handling
them fails unless PKGBUILD is in the $PWD.
fix placement and recovery of the build product

makepkg puts the build product in ${PKGDEST-$PWD}, PKGDEST was not
set, and PWD=$TOPDIR/SOURCES, but recipe_build_arch() was looking
in $TOPDIR/BUILD.

half of recipe_build_arch() is replaced by PKGDEST=$TOPDIR/ARCHPKGS.
makepkg commandline shorter with --config ...

it's easier to read and tweak this way.