make it possible to profile gotweb; tracey had the same diff

make tmp dir location a compile-time setting and change gotweb's tmp dir We are not sure whether a gotweb package can own /var/www/tmp on OpenBSD. Moving gotweb's tmp dir to /var/www/got/tmp sidesteps that issue.

add conditional variable assignment operator to CHROOT_DIR

ensure that we always install static binaries to gotweb's chroot Compile static libexec binaries for gotweb, keeping them separate from the main build. Use the same source files but a separate set of Makefiles. Previously, 'make web-install' installed whichever libexec binaries had already been built, and if those happened to be dynamically linked they failed to run inside the chroot which resulted in "privsep peer process closed pipe" being rendered on the index page.