Add target to use LLVM wasm backend

The new target is wasm32-experimental-emscripten. Adds a new
configuration option to opt in to building experimental LLVM backends
such as the WebAssembly backend. The target name was chosen to be
similar to the existing wasm32-unknown-emscripten target so that the
build and tests would work with minimal other code changes. When/if the
new target replaces the old target, simply renaming it should just work.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/bootstrap/config.toml.example b/src/bootstrap/config.toml.example
index 3a467dafbfb..7a52222e46e 100644
--- a/src/bootstrap/config.toml.example
+++ b/src/bootstrap/config.toml.example
@@ -53,6 +53,14 @@
 # Rust team and file an issue if you need assistance in porting!
 #targets = "X86;ARM;AArch64;Mips;PowerPC;SystemZ;JSBackend;MSP430;Sparc;NVPTX;Hexagon"
 
+# LLVM experimental targets to build support for. These targets are specified in
+# the same format as above, but since these targets are experimental, they are
+# not built by default and the experimental Rust compilation targets that depend
+# on them will not work unless the user opts in to building them. Possible
+# experimental LLVM targets include WebAssembly for the
+# wasm32-experimental-emscripten Rust target.
+#experimental-targets = ""
+
 # Cap the number of parallel linker invocations when compiling LLVM.
 # This can be useful when building LLVM with debug info, which significantly
 # increases the size of binaries and consequently the memory required by