Kill asmjs-unknown-emscripten

asmjs has been in limbo for years. Modern rustc does not even
acknowledge it as an existing target anymore. As such, reap it out.

This commit also removes emscripten.sh, which has not been used anywhere
even prior to this change.

Author: purplesyringa

.changes/1609.json

@@ -0,0 +1,5 @@
+{
+    "description": "remove `asmjs-unknown-emscripten` target.",
+    "type": "removed",
+    "breaking": true
+}

README.md

@@ -261,7 +261,6 @@ terminate.
 | `x86_64-unknown-linux-gnu:centos` [5]  | 2.17   | 4.8.5  | ✓   | 4.2.1 |   ✓    |
 | `x86_64-unknown-linux-musl`            | 1.2.3  | 9.2.0  | ✓   | N/A   |   ✓    |
 | `x86_64-unknown-netbsd` [3]            | 9.2.0  | 9.4.0  | ✓   | N/A   |        |
-<!--| `asmjs-unknown-emscripten` [7]       | 3.1.14 | 15.0.0  | ✓   | N/A   |   ✓    |-->
 
 [1] libc = bionic; Only works with native tests, that is, tests that do not
     depends on the Android Runtime. For i686 some tests may fails with the

docker/Dockerfile.asmjs-unknown-emscripten

@@ -152,7 +152,6 @@ impl TargetTriple {
             "x86_64-linux-android" => None,
             "x86_64-pc-windows-gnu" => None,
             "i686-pc-windows-gnu" => None,
-            "asmjs-unknown-emscripten" => None,
             "wasm32-unknown-emscripten" => None,
             "x86_64-unknown-dragonfly" => Some("dragonflybsd-amd64"),
             "i686-unknown-freebsd" => Some("freebsd-i386"),

docker/emscripten.sh

@@ -402,15 +402,6 @@ cpp = true
 std = true
 run = true
 
-[[target]]
-# Disabled for now, see https://github.com/rust-lang/rust/issues/98216 & https://github.com/cross-rs/cross/issues/634
-disabled = true
-target = "asmjs-unknown-emscripten"
-os = "ubuntu-latest"
-cpp = true
-std = true
-run = true
-
 [[target]]
 target = "wasm32-unknown-emscripten"
 os = "ubuntu-latest"