Revert "Changes a few compile options for the new emscripten (3.1.70)" (#917)

Reverts flutter/buildroot#916

build/config/compiler/BUILD.gn

diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 61e54bb..608e36a 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -292,8 +292,6 @@
       "NO_EXIT_RUNTIME=1",
       "-s",
       "STRICT=1",
-      "-s",
-      "ENVIRONMENT=web,worker",
 
       # Reduces global namespace pollution.
       "-s",

build/toolchain/wasm.gni

diff --git a/build/toolchain/wasm.gni b/build/toolchain/wasm.gni
index 7994057..1e4b953 100644
--- a/build/toolchain/wasm.gni
+++ b/build/toolchain/wasm.gni
@@ -62,6 +62,11 @@
       "{{root_out_dir}}/{{target_output_name}}.js.symbols",
     ]
 
+    if (wasm_use_pthreads || (defined(extra_toolchain_args.wasm_use_pthreads) &&
+                              extra_toolchain_args.wasm_use_pthreads)) {
+      link_outputs += [ "{{root_out_dir}}/{{target_output_name}}.worker.js" ]
+    }
+
     if (is_debug && !wasm_use_dwarf) {
       link_outputs += [ "{{root_out_dir}}/{{target_output_name}}.wasm.map" ]
     }