[WebAssembly] Add WebAssembly to LLVM_ALL_TARGTS.
[WebAssembly] Add WebAssembly to LLVM_ALL_TARGTS.

This makes WebAssembly build by default, rather than requiring
LLVM_EXPERIMENTAL_TARGETS_TO_BUILD!

Differential Revision: https://reviews.llvm.org/D43211


git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@342701 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,apple/swift-llvm