build: Disable valgrind by default on the Mac. Our suppressions file doesn't even begin to cover the huge stream of errors that dyld generates.

Since moving to a downloadable snapshot for stage0, it's been
possible to complete the build without compiling code written
in ocaml. However, the configure script still required it to
be present.

This commit changes detection failure to a non-fatal condition,
allowing the build to complete on systems without an ocaml
compiler.

An info message is also made conditional.

NOTE: all 'long' parameters now use a double dash, so --shared, rather
than gcc-style -shared.

wrong on Windows.

building rustllvm.

symbols because of an Object.o in a .a and one outside. A similar
problem happens for the non-shared part of libpthread.

This patch moves the -whole-archive/-no-whole-archive to include just the
llvm libs.

Fix error where make check would not produce compilers first, due to make's infinite-recursion-prevention heuristic.

Um, that'd be, align the word *before* retpc. Addresses point to the low part of a word. Un-XFAIL nbody on Darwin.