This addresses part of #713, by listing and building C libraries as
dependencies. This means we automatically build CLAPACK when needed, and
`lxml`'s C dependencies are not built if lxml is not. In particular,
building "core" should now be faster.
The building itself is still performed by Makefile.
The biggest change is that most of `0001-hacks-for-WebAssembly-build.patch` is eliminated, and the remaining is split up into individual single-purpose patches with corresponding documentation.
Most of `0001-hacks-for-WebAssembly-build.patch` is in fact unnecessary. We can continue to produce `.a` files instead of `.bc` files, and all we have to do to make it build is to set `$(ARCH) = emar` and `$(RANLIB) = emranlib`. In fact, we don't have to set them to anything, since the point of emmake is to set these for us (except emmake uses `$(AR)` so we set `$(ARCH) = $(AR)`).
There are places where `ar` and `cc` etc. are used directly instead of the variables; we use `sed` to fix this in the parent `Makefile` instead of patching.
In addition, there are also the following changes:
- Change the build system to build CLAPACK-WA/INSTALL as well. We should always have built it, but we managed to get away with not doing so due to a bug in emscripten that is fixed in 1.38.43. See https://github.com/iodide-project/pyodide/pull/843#issuecomment-744428471
- Generate `F2CLIB/libf2c/arith.h` properly instead of setting it to an empty file.
- Remove a seemingly unnecessary patch (945f06c46e)
Dexter Chua