HyperRogue 13.1o, mymake (the project's own build tool) for the current Emscripten (6.0.10).

- em++ from the PATH (emsdk_env.sh) instead of /usr/lib/emscripten/em++;
- EXTRA_EXPORTED_RUNTIME_METHODS was removed from Emscripten (it is now an error); the same list
  goes in EXPORTED_RUNTIME_METHODS.

Part of the source of the build served at fredygames.com (GPL-2.0-or-later, like HyperRogue).

--- a/mymake.cpp
+++ b/mymake.cpp
@@ -126,14 +126,14 @@
   }
 
 void set_web() {
-  preprocessor = "/usr/lib/emscripten/em++ -E";
-  compiler = "/usr/lib/emscripten/em++ -c -Wno-invalid-offsetof";
+  preprocessor = "em++ -E";
+  compiler = "em++ -c -Wno-invalid-offsetof";
   default_standard = standard = " -std=c++17";
   opts = "-DISWEB=1";
   linker = 
-    "/usr/lib/emscripten/em++ -O2 -s USE_ZLIB=1 -s DISABLE_DEPRECATED_FIND_EVENT_TARGET_BEHAVIOR=0 -s TOTAL_MEMORY=512MB "
+    "em++ -O2 -s USE_ZLIB=1 -s DISABLE_DEPRECATED_FIND_EVENT_TARGET_BEHAVIOR=0 -s TOTAL_MEMORY=512MB "
     "-s STACK_SIZE=1048576 "
-    "-s EXTRA_EXPORTED_RUNTIME_METHODS='[\"FS\",\"ccall\"]' "
+    "-s EXPORTED_RUNTIME_METHODS='[\"FS\",\"ccall\"]' "
     "-s EXPORTED_FUNCTIONS=\"['_main', '_use_file']\" "
     "-s DISABLE_EXCEPTION_CATCHING=0";
   default_exec_name = "mhyper.html";