[SH]CMakeLists.txt: disable Boost.Context under Emscripten

CMakeLists.txt

@@ -269,9 +269,6 @@ set(ANDROID_LINUX_PERF_PATH ""
 set(HERMES_MSVC_MP ON CACHE STRING
   "Enable /MP in MSVC for parallel builds")
 
-set(EMSCRIPTEN_FASTCOMP OFF CACHE BOOL
-  "Emscripten is using the fastcomp backend instead of the LLVM one")
-
 set(HERMES_ENABLE_INTL OFF CACHE BOOL
   "Enable JS Intl support (WIP)")
 
@@ -532,7 +529,7 @@ if (HERMES_ALLOW_BOOST_CONTEXT EQUAL 0)
 elseif (HERMES_ALLOW_BOOST_CONTEXT EQUAL 2)
     set(HERMES_USE_BOOST_CONTEXT 1)
 elseif (HERMES_ALLOW_BOOST_CONTEXT EQUAL 1)
-    if (HERMES_ENABLE_ADDRESS_SANITIZER)
+    if (HERMES_ENABLE_ADDRESS_SANITIZER OR EMSCRIPTEN)
         set(HERMES_USE_BOOST_CONTEXT 0)
     else()
         set(HERMES_USE_BOOST_CONTEXT 1)