Revert "SysTools: make various functions thread-safe"

This reverts commit 376719e768f7e9167489341a16b3343f22ab322e.

This is not necessary because the parallel upsweep uses thread-local
temporary files.
Atomically update global mutable state in a few places
Binary: Make lazyGet more thread-safe

All values read lazily from the same BinHandle share the same mutable
offset variable (_off_r). If two such lazy values are simultaneously
evaluated, the two threads will step over each other when writing to
_off_r.

Fortunately, for BinMem handles, making lazyGet thread-safe is simple:
just use a fresh off_r variable when deferring the call to getAt.

For BinIO handles, a race condition still exists because IO handles
contain their own mutable file pointer variable that gets clobbered in a
similar way that _off_r would. But GHC doesn't use BinIO handles anywhere
so this particular issue could be ignored for now.
TcEnv: Make mkWrapperName deterministic and thread-safe
Make stdout and stderr line-buffered

An unbuffered handle is very slow to output to and there doesn't seem to
be any reason to have these handles unbuffered.
Implement the parallel upsweep and the -j flag