tests: use "env builtin" in place of "$abs_top_builddir/src/builtin"

tests: use "env builtin" in place of "$abs_top_builddir/src/builtin"

This works for any program that might also be a shell built-in.
It is more concise.  In addition, it makes output more reproducible:
some diagnostics include argv[0], which will now be just the program
name, rather than the full absolute name of the executable.
* tests/misc/sort-compress.sh: Use env kill, rather than absolute name.
* tests/install/trap.sh: Likewise.
* tests/misc/timeout.sh: Likewise.
* tests/touch/no-dereference.sh: Do the same for two uses of "test".
* tests/touch/no-create-missing.sh: Likewise.