fbc/emscripten: pass -sASYNCIFY at link-time not compile-time

It is a link-time flag and does nothing at compile-time. I think this has
changed since earlier Emscripten versions, due to Emscripten's new wasm backend.

changelog.txt

@@ -11,6 +11,7 @@ Version 1.10.1
 - fbc: emscripten: wstring was broken because sizeof(wstring) was 2 rather than 4
 - emscripten: non-graphical programs will now run under node.js. Use -x output.js to produce a .js rather than an .html
 - rtlib: emscripten: CURDIR and EXEPATH always returned ""
+- emscripten/fbc: -sASYNCIFY wasn't passed to emcc at link-time as needed by recent Emscripten
 
 
 Version 1.10.0

src/compiler/fbc.bas

@@ -898,7 +898,8 @@ private function hLinkFiles( ) as integer
 			"CASE_INSENSITIVE_FS=1", _
 			"TOTAL_MEMORY=67108864", _
 			"ALLOW_MEMORY_GROWTH=1", _
-			"RETAIN_COMPILER_SETTINGS=1" _
+			"RETAIN_COMPILER_SETTINGS=1", _
+			"ASYNCIFY=1" _
 		}
 			'"WARN_UNALIGNED=1", _
 
@@ -3443,7 +3444,7 @@ private function hCompileStage2Module( byval module as FBCIOFILE ptr ) as intege
 			'if Emscripten is used, we will skip the assembly generation and compile directly to object code
 			ln += "-c -nostdlib -nostdinc -Wall -Wno-unused-label " + _
 				"-Wno-unused-function -Wno-unused-variable "
-			ln += "-Wno-warn-absolute-paths -s ASYNCIFY=1 -s RETAIN_COMPILER_SETTINGS=1 "
+			ln += "-Wno-warn-absolute-paths "
 		end if
 
 		'' Don't warn about non-standard main() signature

tests/unit-tests.mk

@@ -122,7 +122,7 @@ ifdef TARGET
 endif
 ifeq ($(TARGET_OS),js)
 # Copy the file/ and data/ directories into the in-memory FS
-	FBC_LFLAGS += -Wl -sASYNCIFY,-sEXIT_RUNTIME -Wl --preload-file,file,--preload-file,data
+	FBC_LFLAGS += -Wl -sEXIT_RUNTIME -Wl --preload-file,file,--preload-file,data
 endif
 
 ifeq ($(ENABLE_CHECK_BUGS),1)