haskell-src-exts: set -mcpu flag for LLVM

Signed-off-by: Nicola Squartini <tensor5@gmail.com>
haskell-src-exts.pkgbuild: use uname -m

Signed-off-by: Nicola Squartini <tensor5@gmail.com>
Bump haskell-src-exts and its dependants.

Closes #148

Signed-off-by: Magnus Therning <magnus@therning.org>